diff --git a/examples/category_manager/get_categories.py b/examples/category_manager/get_categories.py
index e16b4b1..1242711 100644
--- a/examples/category_manager/get_categories.py
+++ b/examples/category_manager/get_categories.py
@@ -1,4 +1,5 @@
 import os
+from typing import List
 
 from dotenv import load_dotenv
 
@@ -27,6 +28,6 @@
     # print(get_categories_response)
 
     # Print the API response containing the categories
-    categories: list[Category] = get_categories_response.get_data()
+    categories: List[Category] = get_categories_response.get_data()
 
     print(categories)
diff --git a/examples/gateway_manager/get_gateways.py b/examples/gateway_manager/get_gateways.py
index 1550f2e..e7d4288 100644
--- a/examples/gateway_manager/get_gateways.py
+++ b/examples/gateway_manager/get_gateways.py
@@ -1,4 +1,5 @@
 import os
+from typing import List
 
 from dotenv import load_dotenv
 
@@ -28,6 +29,6 @@
     # print(get_gateways_response)
 
     # Extract the listing of gateways from the response
-    gatewayListing: list[Gateway] = get_gateways_response.get_data()
+    gatewayListing: List[Gateway] = get_gateways_response.get_data()
 
     print(gatewayListing)
diff --git a/pyproject.toml b/pyproject.toml
index 40cb0e0..76df706 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -98,7 +98,6 @@ extend-safe-fixes = [
     "D415", # docstrings should end with a period, question mark, or exclamation point
 ]
 ignore = [
-    "ANN001",
     "ANN003",
     "ANN101", # missing type annotation for self
     "ANN102", # missing type annotation for cls
diff --git a/src/multisafepay/api/base/abstract_manager.py b/src/multisafepay/api/base/abstract_manager.py
index b81d2da..7d3f06c 100644
--- a/src/multisafepay/api/base/abstract_manager.py
+++ b/src/multisafepay/api/base/abstract_manager.py
@@ -5,6 +5,7 @@
 
 # See the DISCLAIMER.md file for disclaimer details.
 
+
 from multisafepay.client.client import Client
 
 
diff --git a/src/multisafepay/api/base/decorator.py b/src/multisafepay/api/base/decorator.py
index 06bf044..2a1381f 100644
--- a/src/multisafepay/api/base/decorator.py
+++ b/src/multisafepay/api/base/decorator.py
@@ -281,7 +281,7 @@ def adapt_brands(
 
         Parameters
         ----------
-        brands (Optional[list[Optional[dict]]]): A list of dictionaries containing brand information, by default None.
+        brands (Optional[List[Optional[dict]]]): A list of dictionaries containing brand information, by default None.
 
         Returns
         -------
diff --git a/src/multisafepay/api/base/listings/listing.py b/src/multisafepay/api/base/listings/listing.py
index 34d04b3..0277d5f 100644
--- a/src/multisafepay/api/base/listings/listing.py
+++ b/src/multisafepay/api/base/listings/listing.py
@@ -30,7 +30,7 @@ def __init__(self, data: List[Any], class_type: type, **kwargs):
 
         Parameters
         ----------
-        data (list[Any]): A list of data to be converted into items of type T.
+        data (List[Any]): A list of data to be converted into items of type T.
         class_type (type): The class type to convert the data into.
         **kwargs: Additional keyword arguments to pass to the class type constructor.
 
@@ -59,7 +59,7 @@ def __iter__(self):
         """
         return iter(self.data)
 
-    def __getitem__(self, index):
+    def __getitem__(self: "Listing", index: int) -> T:
         """
         Get an item by index.
 
diff --git a/src/multisafepay/api/base/response/custom_api_response.py b/src/multisafepay/api/base/response/custom_api_response.py
index f37f839..6569ad3 100644
--- a/src/multisafepay/api/base/response/custom_api_response.py
+++ b/src/multisafepay/api/base/response/custom_api_response.py
@@ -22,7 +22,7 @@ class CustomApiResponse(ApiResponse):
 
     data: Optional[Any]
 
-    def __init__(self, data, **kwargs):
+    def __init__(self: "CustomApiResponse", data: Optional[Any], **kwargs):
         """
         Initialize the CustomApiResponse with optional data and additional keyword arguments.
 
diff --git a/src/multisafepay/api/paths/auth/auth_manager.py b/src/multisafepay/api/paths/auth/auth_manager.py
index 3ade070..994fcd9 100644
--- a/src/multisafepay/api/paths/auth/auth_manager.py
+++ b/src/multisafepay/api/paths/auth/auth_manager.py
@@ -12,6 +12,7 @@
     CustomApiResponse,
 )
 from multisafepay.api.paths.auth.api_token.response.api_token import ApiToken
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -21,13 +22,13 @@ class AuthManager(AbstractManager):
     A manager class for handling authentication-related operations.
     """
 
-    def __init__(self, client):
+    def __init__(self: "AuthManager", client: Client):
         """
         Initialize the CaptureManager with a client.
 
         Parameters
         ----------
-            client: The client used to make API requests.
+            client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/capture/capture_manager.py b/src/multisafepay/api/paths/capture/capture_manager.py
index 4b92f5f..39eb568 100644
--- a/src/multisafepay/api/paths/capture/capture_manager.py
+++ b/src/multisafepay/api/paths/capture/capture_manager.py
@@ -16,6 +16,7 @@
     CaptureRequest,
 )
 from multisafepay.api.paths.capture.response.capture import CancelReservation
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -25,13 +26,13 @@ class CaptureManager(AbstractManager):
     A class to manage capture operations.
     """
 
-    def __init__(self, client):
+    def __init__(self: "CaptureManager", client: Client):
         """
         Initialize the CaptureManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/categories/category_manager.py b/src/multisafepay/api/paths/categories/category_manager.py
index 0d0055f..f84caad 100644
--- a/src/multisafepay/api/paths/categories/category_manager.py
+++ b/src/multisafepay/api/paths/categories/category_manager.py
@@ -11,6 +11,7 @@
     CustomApiResponse,
 )
 from multisafepay.api.paths.categories.response.category import Category
+from multisafepay.client.client import Client
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
 
@@ -19,13 +20,13 @@ class CategoryManager(AbstractManager):
     A manager class for handling category-related API requests.
     """
 
-    def __init__(self, client):
+    def __init__(self: "CategoryManager", client: Client):
         """
         Initialize the CategoryManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/gateways/gateway_manager.py b/src/multisafepay/api/paths/gateways/gateway_manager.py
index a9a41ee..c53f83d 100644
--- a/src/multisafepay/api/paths/gateways/gateway_manager.py
+++ b/src/multisafepay/api/paths/gateways/gateway_manager.py
@@ -11,6 +11,7 @@
     CustomApiResponse,
 )
 from multisafepay.api.paths.gateways.response.gateway import Gateway
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -27,7 +28,21 @@ class GatewayManager(AbstractManager):
     Manages gateway-related operations.
     """
 
-    def get_gateways(self, include_coupons: bool = True) -> CustomApiResponse:
+    def __init__(self: "GatewayManager", client: Client):
+        """
+        Initialize the CategoryManager with a client.
+
+        Parameters
+        ----------
+        client (Client): The client used to make API requests.
+
+        """
+        super().__init__(client)
+
+    def get_gateways(
+        self: "GatewayManager",
+        include_coupons: bool = True,
+    ) -> CustomApiResponse:
         """
         Retrieve a list of gateways.
 
diff --git a/src/multisafepay/api/paths/issuers/issuer_manager.py b/src/multisafepay/api/paths/issuers/issuer_manager.py
index 26311bb..cf30635 100644
--- a/src/multisafepay/api/paths/issuers/issuer_manager.py
+++ b/src/multisafepay/api/paths/issuers/issuer_manager.py
@@ -14,6 +14,7 @@
     ALLOWED_GATEWAY_CODES,
     Issuer,
 )
+from multisafepay.client.client import Client
 from multisafepay.exception.invalid_argument import InvalidArgumentException
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -23,13 +24,13 @@ class IssuerManager(AbstractManager):
     Manager class for handling issuer-related operations.
     """
 
-    def __init__(self, client):
+    def __init__(self: "IssuerManager", client: Client):
         """
         Initialize the IssuerManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/me/me_manager.py b/src/multisafepay/api/paths/me/me_manager.py
index 069f3dc..66319e1 100644
--- a/src/multisafepay/api/paths/me/me_manager.py
+++ b/src/multisafepay/api/paths/me/me_manager.py
@@ -11,6 +11,7 @@
     CustomApiResponse,
 )
 from multisafepay.api.paths.me.response.me import Me
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -20,13 +21,13 @@ class MeManager(AbstractManager):
     A manager class for handling 'me' related API requests.
     """
 
-    def __init__(self, client):
+    def __init__(self, client: Client):
         """
         Initialize the MeManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/orders/order_id/refund/request/components/checkout_data.py b/src/multisafepay/api/paths/orders/order_id/refund/request/components/checkout_data.py
index 01d291e..d3eafae 100644
--- a/src/multisafepay/api/paths/orders/order_id/refund/request/components/checkout_data.py
+++ b/src/multisafepay/api/paths/orders/order_id/refund/request/components/checkout_data.py
@@ -20,19 +20,19 @@ class CheckoutData(RequestModel):
 
     Attributes
     ----------
-    items (Optional[list[CartItem]]): The list of cart items.
+    items (Optional[List[CartItem]]): The list of cart items.
 
     """
 
     items: Optional[List[CartItem]]
 
-    def add_items(self, items=[]):
+    def add_items(self, items: List[CartItem] = ()):
         """
         Adds multiple items to the checkout data.
 
         Parameters
         ----------
-        items (list[CartItem]): The list of items to add.
+        items (List[CartItem]): The list of items to add.
 
         Returns
         -------
@@ -45,7 +45,7 @@ def add_items(self, items=[]):
             self.add_item(item)
         return self
 
-    def add_item(self, item):
+    def add_item(self, item: CartItem):
         """
         Adds a single item to the checkout data.
 
@@ -69,7 +69,7 @@ def get_items(self):
 
         Returns
         -------
-        list[CartItem]: The list of items.
+        List[CartItem]: The list of items.
 
         """
         return self.items
@@ -92,7 +92,7 @@ def get_item(self, index: int):
     def generate_from_shopping_cart(
         self,
         shopping_cart: ShoppingCart,
-        tax_table_selector="",
+        tax_table_selector: str = "",
     ):
         """
         Generates checkout data from a shopping cart.
@@ -110,13 +110,17 @@ def generate_from_shopping_cart(
                 shopping_cart_item.add_tax_table_selector(tax_table_selector)
             self.add_item(shopping_cart_item)
 
-    def refund_by_merchant_item_id(self, merchant_item_id, quantity=0):
+    def refund_by_merchant_item_id(
+        self,
+        merchant_item_id: str,
+        quantity: int = 0,
+    ):
         """
         Processes a refund by merchant item ID.
 
         Parameters
         ----------
-        merchant_item_id: The merchant item ID to refund.
+        merchant_item_id (str): The merchant item ID to refund.
         quantity (int): The quantity to refund.
 
         Raises
@@ -139,13 +143,13 @@ def refund_by_merchant_item_id(self, merchant_item_id, quantity=0):
 
         self.add_item(refund_item)
 
-    def get_item_by_merchant_item_id(self, merchant_item_id):
+    def get_item_by_merchant_item_id(self, merchant_item_id: str):
         """
         Retrieves an item by its merchant item ID.
 
         Parameters
         ----------
-        merchant_item_id: The merchant item ID to search for.
+        merchant_item_id (str): The merchant item ID to search for.
 
         Returns
         -------
diff --git a/src/multisafepay/api/paths/orders/order_manager.py b/src/multisafepay/api/paths/orders/order_manager.py
index f516bc0..aa62ef7 100644
--- a/src/multisafepay/api/paths/orders/order_manager.py
+++ b/src/multisafepay/api/paths/orders/order_manager.py
@@ -36,6 +36,7 @@
 from multisafepay.api.paths.orders.response.order_response import Order
 from multisafepay.api.shared.cart.shopping_cart import ShoppingCart
 from multisafepay.api.shared.description import Description
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 from multisafepay.value_object.amount import Amount
@@ -47,13 +48,13 @@ class OrderManager(AbstractManager):
     Manages operations related to orders, such as creating, updating, capturing, and refunding orders.
     """
 
-    def __init__(self, client):
+    def __init__(self, client: Client):
         """
         Initialize the OrderManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/orders/request/order_request.py b/src/multisafepay/api/paths/orders/request/order_request.py
index 9df2bc8..6bd6422 100644
--- a/src/multisafepay/api/paths/orders/request/order_request.py
+++ b/src/multisafepay/api/paths/orders/request/order_request.py
@@ -257,13 +257,13 @@ def add_customer(self, customer: Customer) -> "OrderRequest":
         self.customer = customer
         return self
 
-    def add_gateway(self, gateway) -> "OrderRequest":
+    def add_gateway(self, gateway: str) -> "OrderRequest":
         """
         Adds the gateway to the order request.
 
         Parameters
         ----------
-        gateway: The gateway.
+        gateway (str): The gateway.
 
         Returns
         -------
diff --git a/src/multisafepay/api/paths/orders/response/order_response.py b/src/multisafepay/api/paths/orders/response/order_response.py
index 8a89950..6ae6555 100644
--- a/src/multisafepay/api/paths/orders/response/order_response.py
+++ b/src/multisafepay/api/paths/orders/response/order_response.py
@@ -36,7 +36,7 @@ class Order(ResponseModel):
     amount (Optional[int]): The amount of the order.
     amount_refunded (Optional[int]): The amount refunded.
     checkout_options (Optional[CheckoutOptions]): The checkout options.
-    costs (Optional[list[Costs]]): The costs of the order.
+    costs (Optional[List[Costs]]): The costs of the order.
     created (Optional[str]): The creation date of the order.
     modified (Optional[str]): The modification date of the order.
     currency (Optional[str]): The currency of the order.
@@ -50,10 +50,10 @@ class Order(ResponseModel):
     order_id (Optional[str]): The ID of the order.
     order_total (Optional[float]): The total amount of the order.
     payment_details (Optional[PaymentDetails]): The payment details.
-    payment_method (Optional[list[PaymentMethod]]): The payment methods.
+    payment_method (Optional[List[PaymentMethod]]): The payment methods.
     reason (Optional[str]): The reason for the order.
     reason_code (Optional[str]): The reason code for the order.
-    related_transactions (Optional[list[Transaction]]): The related transactions.
+    related_transactions (Optional[List[Transaction]]): The related transactions.
     shopping_cart (Optional[ShoppingCart]): The shopping cart.
     status (Optional[str]): The status of the order.
     transaction_id (Optional[str]): The ID of the transaction.
diff --git a/src/multisafepay/api/paths/payment_methods/payment_method_manager.py b/src/multisafepay/api/paths/payment_methods/payment_method_manager.py
index e367b96..22e43c0 100644
--- a/src/multisafepay/api/paths/payment_methods/payment_method_manager.py
+++ b/src/multisafepay/api/paths/payment_methods/payment_method_manager.py
@@ -13,7 +13,7 @@
 from multisafepay.api.paths.payment_methods.response.payment_method import (
     PaymentMethod,
 )
-from multisafepay.client.client import ApiResponse
+from multisafepay.client.client import ApiResponse, Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -30,13 +30,13 @@ class PaymentMethodManager(AbstractManager):
     A class representing the PaymentMethodManager.
     """
 
-    def __init__(self, client):
+    def __init__(self, client: Client):
         """
         Initialize the CaptureManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/paths/payment_methods/response/components/brand.py b/src/multisafepay/api/paths/payment_methods/response/components/brand.py
index a8f7722..bbade26 100644
--- a/src/multisafepay/api/paths/payment_methods/response/components/brand.py
+++ b/src/multisafepay/api/paths/payment_methods/response/components/brand.py
@@ -20,7 +20,7 @@ class Brand(ResponseModel):
 
     Attributes
     ----------
-    allowed_countries (Optional[list[str]]): The allowed countries for the brand.
+    allowed_countries (Optional[List[str]]): The allowed countries for the brand.
     icon_urls (Optional[IconUrls]): The icon URLs for the brand.
     id (Optional[str]): The ID of the brand.
     name (Optional[str]): The name of the brand.
diff --git a/src/multisafepay/api/paths/payment_methods/response/payment_method.py b/src/multisafepay/api/paths/payment_methods/response/payment_method.py
index ee459af..8d5a080 100644
--- a/src/multisafepay/api/paths/payment_methods/response/payment_method.py
+++ b/src/multisafepay/api/paths/payment_methods/response/payment_method.py
@@ -35,17 +35,17 @@ class PaymentMethod(ResponseModel):
     ----------
     additional_data (Optional[dict]): Additional data for the payment method.
     allowed_amount (Optional[AllowedAmount]): The allowed amount for the payment method.
-    allowed_countries (Optional[list[str]]): The allowed countries for the payment method.
-    allowed_currencies (Optional[list[str]]): The allowed currencies for the payment method.
+    allowed_countries (Optional[List[str]]): The allowed countries for the payment method.
+    allowed_currencies (OptionalList[str]]): The allowed currencies for the payment method.
     apps (Optional[Apps]): The apps associated with the payment method.
-    brands (Optional[list[Brand]]): The brands associated with the payment method.
+    brands (Optional[List[Brand]]): The brands associated with the payment method.
     description (Optional[str]): The description of the payment method.
     icon_urls (Optional[IconUrls]): The icon URLs for the payment method.
     id (Optional[str]): The ID of the payment method.
     label (Optional[str]): The label of the payment method.
     name (Optional[str]): The name of the payment method.
-    preferred_countries (Optional[list[str]]): The preferred countries for the payment method.
-    required_customer_data (Optional[list[str]]): The required customer data for the payment method.
+    preferred_countries (Optional[List[str]]): The preferred countries for the payment method.
+    required_customer_data (Optional[List[str]]): The required customer data for the payment method.
     tokenization (Optional[Tokenization]): The tokenization support information for the payment method.
     type (Optional[str]): The type of the payment method.
     shopping_cart_required (Optional[bool]): Whether a shopping cart is required for the payment method.
diff --git a/src/multisafepay/api/paths/recurring/recurring_manager.py b/src/multisafepay/api/paths/recurring/recurring_manager.py
index d5f372b..d8b16e0 100644
--- a/src/multisafepay/api/paths/recurring/recurring_manager.py
+++ b/src/multisafepay/api/paths/recurring/recurring_manager.py
@@ -5,6 +5,7 @@
 
 # See the DISCLAIMER.md file for disclaimer details.
 
+from typing import Any
 
 from multisafepay.api.base.abstract_manager import AbstractManager
 from multisafepay.api.base.response.api_response import ApiResponse
@@ -14,6 +15,7 @@
 from multisafepay.api.paths.recurring.customer_reference.token.token import (
     Token,
 )
+from multisafepay.client.client import Client
 from multisafepay.util.dict_utils import dict_empty
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
@@ -33,7 +35,7 @@ class RecurringManager(AbstractManager):
     CREDIT_CARD_GATEWAY_CODE = "CREDITCARD"
     CREDIT_CARD_GATEWAYS = ["VISA", "MASTERCARD", "AMEX", "MAESTRO"]
 
-    def __init__(self, client):
+    def __init__(self, client: Client):
         """
         Initializes the RecurringManager with a client.
 
@@ -43,7 +45,7 @@ def __init__(self, client):
 
         """
         super().__init__(client)
-        self.tokens = {}
+        self.tokens: Any = {}
 
     def get_list(
         self,
diff --git a/src/multisafepay/api/paths/transactions/response/transaction.py b/src/multisafepay/api/paths/transactions/response/transaction.py
index 2e0e43e..04ae288 100644
--- a/src/multisafepay/api/paths/transactions/response/transaction.py
+++ b/src/multisafepay/api/paths/transactions/response/transaction.py
@@ -23,7 +23,7 @@ class Transaction(ResponseModel):
     ----------
     amount (Optional[int]): The amount of the transaction.
     completed (Optional[str]): The completion date of the transaction.
-    costs (Optional[list[Costs]]): The costs of the transaction.
+    costs (Optional[List[Costs]]): The costs of the transaction.
     created (Optional[str]): The creation date of the transaction.
     modified (Optional[str]): The modification date of the transaction.
     currency (Optional[str]): The currency of the transaction.
@@ -36,7 +36,7 @@ class Transaction(ResponseModel):
     net (Optional[int]): The net amount of the transaction.
     order_id (Optional[str]): The order ID of the transaction.
     payment_method (Optional[str]): The payment method of the transaction.
-    payment_methods (Optional[list[PaymentMethod]]): The payment methods of the transaction.
+    payment_methods (Optional[List[PaymentMethod]]): The payment methods of the transaction.
     reason (Optional[str]): The reason for the transaction.
     reason_code (Optional[str]): The reason code for the transaction.
     site_id (Optional[str]): The site ID of the transaction.
diff --git a/src/multisafepay/api/paths/transactions/transaction_manager.py b/src/multisafepay/api/paths/transactions/transaction_manager.py
index 939baf1..3060b56 100644
--- a/src/multisafepay/api/paths/transactions/transaction_manager.py
+++ b/src/multisafepay/api/paths/transactions/transaction_manager.py
@@ -16,6 +16,7 @@
 from multisafepay.api.paths.transactions.response.transaction import (
     Transaction,
 )
+from multisafepay.client.client import Client
 from multisafepay.util.message import MessageList, gen_could_not_created_msg
 
 ALLOWED_OPTIONS = {
@@ -40,13 +41,13 @@ class TransactionManager(AbstractManager):
     A class representing the TransactionManager.
     """
 
-    def __init__(self, client):
+    def __init__(self, client: Client):
         """
         Initialize the CaptureManager with a client.
 
         Parameters
         ----------
-        client: The client used to make API requests.
+        client (Client): The client used to make API requests.
 
         """
         super().__init__(client)
diff --git a/src/multisafepay/api/shared/cart/cart_item.py b/src/multisafepay/api/shared/cart/cart_item.py
index fd3f667..d3ef30e 100644
--- a/src/multisafepay/api/shared/cart/cart_item.py
+++ b/src/multisafepay/api/shared/cart/cart_item.py
@@ -26,7 +26,7 @@ class CartItem(ApiModel):
     image: (Optional[str]) The image URL.
     merchant_item_id: (Optional[str]) The merchant item ID.
     name: (Optional[str]) The name.
-    options: (Optional[list[dict]]) The list of options.
+    options: (Optional[List[dict]]) The list of options.
     product_url: (Optional[str]) The product URL.
     quantity: (Optional[int]) The quantity.
     tax_table_selector: (Optional[str]) The tax table selector.
@@ -150,7 +150,7 @@ def add_options(self, options: List[Dict]) -> "CartItem":
 
         Parameters
         ----------
-        options: (list[dict]) The list of options to be added.
+        options: (List[dict]) The list of options to be added.
 
         Returns
         -------
diff --git a/src/multisafepay/api/shared/cart/shopping_cart.py b/src/multisafepay/api/shared/cart/shopping_cart.py
index cac3d32..510dc3f 100644
--- a/src/multisafepay/api/shared/cart/shopping_cart.py
+++ b/src/multisafepay/api/shared/cart/shopping_cart.py
@@ -17,7 +17,7 @@ class ShoppingCart(ApiModel):
 
     Attributes
     ----------
-    items: (Optional[list[CartItem]]) The list of items in the shopping cart.
+    items: (Optional[List[CartItem]]) The list of items in the shopping cart.
 
     """
 
@@ -29,7 +29,7 @@ def get_items(self) -> List[CartItem]:
 
         Returns
         -------
-        list[CartItem]: The list of items in the shopping cart.
+        List[CartItem]: The list of items in the shopping cart.
 
         """
         return self.items
@@ -40,7 +40,7 @@ def add_items(self, items: List[CartItem]):
 
         Parameters
         ----------
-        items: (list[CartItem]) The list of items to be added to the shopping cart.
+        items: (List[CartItem]) The list of items to be added to the shopping cart.
 
         Returns
         -------
diff --git a/src/multisafepay/api/shared/checkout/checkout_options.py b/src/multisafepay/api/shared/checkout/checkout_options.py
index f545bd2..69fc02f 100644
--- a/src/multisafepay/api/shared/checkout/checkout_options.py
+++ b/src/multisafepay/api/shared/checkout/checkout_options.py
@@ -20,7 +20,7 @@ class CheckoutOptions(ApiModel):
     Attributes
     ----------
     default (Optional[DefaultTaxRate]): The default tax rate.
-    alternate (Optional[list[TaxRate]]): A list of alternate tax rates.
+    alternate (Optional[List[TaxRate]]): A list of alternate tax rates.
 
     """
 
@@ -49,7 +49,7 @@ def add_alternate(self, alternate: List[TaxRule]) -> "CheckoutOptions":
 
         Parameters
         ----------
-        alternate (list[TaxRule]): The list of alternate tax rates to be added.
+        alternate (List[TaxRule]): The list of alternate tax rates to be added.
 
         Returns
         -------
diff --git a/src/multisafepay/api/shared/checkout/tax_rule.py b/src/multisafepay/api/shared/checkout/tax_rule.py
index 49278bb..14a5799 100644
--- a/src/multisafepay/api/shared/checkout/tax_rule.py
+++ b/src/multisafepay/api/shared/checkout/tax_rule.py
@@ -19,7 +19,7 @@ class TaxRule(ApiModel):
     Attributes
     ----------
     name (Optional[str]): The name of the tax rule.
-    rules (Optional[list[TaxRate]]): A list of tax rates associated with the tax rule.
+    rules (Optional[List[TaxRate]]): A list of tax rates associated with the tax rule.
     standalone (Optional[bool]): Indicates if the tax rule is standalone.
 
     """
@@ -50,7 +50,7 @@ def add_rules(self, rules: List[TaxRate]) -> "TaxRule":
 
         Parameters
         ----------
-        rules (list[TaxRate]): The list of tax rates to be added.
+        rules (List[TaxRate]): The list of tax rates to be added.
 
         Returns
         -------
diff --git a/src/multisafepay/util/dict_utils.py b/src/multisafepay/util/dict_utils.py
index ce241d1..b2fd58f 100644
--- a/src/multisafepay/util/dict_utils.py
+++ b/src/multisafepay/util/dict_utils.py
@@ -5,10 +5,10 @@
 
 # See the DISCLAIMER.md file for disclaimer details.
 
-from typing import Any, Optional, Union
+from typing import Any, Optional
 
 
-def merge_recursive(dict1, dict2):
+def merge_recursive(dict1: dict, dict2: dict):
     """
     Recursively merge two dictionaries.
 
@@ -66,7 +66,7 @@ def remove_null_recursive(input_data: dict) -> dict:
 
     """
 
-    def process_value(value) -> Optional[Union[dict, list, Any]]:
+    def process_value(value: Any) -> Optional[Any]:
         if isinstance(value, dict):
             processed_dict = remove_null_recursive(value)
             return processed_dict if processed_dict else None
@@ -85,7 +85,7 @@ def process_value(value) -> Optional[Union[dict, list, Any]]:
     }
 
 
-def dict_empty(value) -> bool:
+def dict_empty(value: Any) -> bool:
     """
     Check if the given value is an empty dictionary.
 
diff --git a/src/multisafepay/util/message.py b/src/multisafepay/util/message.py
index a7a39ce..3489437 100644
--- a/src/multisafepay/util/message.py
+++ b/src/multisafepay/util/message.py
@@ -47,7 +47,7 @@ def __iter__(self):
         """
         return iter(self.__root__)
 
-    def __getitem__(self, index):
+    def __getitem__(self, index: int):
         """
         Get a message by index.
 
diff --git a/src/multisafepay/util/total_amount.py b/src/multisafepay/util/total_amount.py
index b7613cf..e8f8edd 100644
--- a/src/multisafepay/util/total_amount.py
+++ b/src/multisafepay/util/total_amount.py
@@ -85,7 +85,7 @@ def __get_tax_rate_by_item(
 
     Returns
     -------
-    int | list[int | Any] | Any: The tax rate for the item, or 0 if no tax rate is found.
+    int | List[int | Any] | Any: The tax rate for the item, or 0 if no tax rate is found.
 
     """
     if "tax_table_selector" not in item or not item["tax_table_selector"]:
diff --git a/src/multisafepay/value_object/country.py b/src/multisafepay/value_object/country.py
index bb06b0c..11ce34c 100644
--- a/src/multisafepay/value_object/country.py
+++ b/src/multisafepay/value_object/country.py
@@ -22,7 +22,7 @@ class Country(BaseModel):
     code: str
 
     @validator("code")
-    def validate_country(cls, value):
+    def validate_country(cls, value: str):
         """
         Validate the country code.
 
diff --git a/src/multisafepay/value_object/currency.py b/src/multisafepay/value_object/currency.py
index 4161b29..4da8fcb 100644
--- a/src/multisafepay/value_object/currency.py
+++ b/src/multisafepay/value_object/currency.py
@@ -24,7 +24,7 @@ class Currency(InmutableModel):
     currency: str
 
     @validator("currency")
-    def validate_currency(cls, value):
+    def validate_currency(cls, value: str):
         """
         Validate the currency code.
 
diff --git a/src/multisafepay/value_object/email_address.py b/src/multisafepay/value_object/email_address.py
index 5c8c39f..7d5324c 100644
--- a/src/multisafepay/value_object/email_address.py
+++ b/src/multisafepay/value_object/email_address.py
@@ -26,7 +26,7 @@ class EmailAddress(InmutableModel):
     email_address: str
 
     @validator("email_address")
-    def validate_email_address(cls, value):
+    def validate_email_address(cls, value: str):
         """
         Validate the email address value.
 
diff --git a/src/multisafepay/value_object/gender.py b/src/multisafepay/value_object/gender.py
index 0df7290..b23e266 100644
--- a/src/multisafepay/value_object/gender.py
+++ b/src/multisafepay/value_object/gender.py
@@ -26,7 +26,7 @@ class Gender(InmutableModel):
     gender: str
 
     @validator("gender")
-    def validate_ip_address(cls, value):
+    def validate_ip_address(cls, value: str):
         """
         Validate the gender value.
 
diff --git a/src/multisafepay/value_object/iban_number.py b/src/multisafepay/value_object/iban_number.py
index b60cf3c..5583e96 100644
--- a/src/multisafepay/value_object/iban_number.py
+++ b/src/multisafepay/value_object/iban_number.py
@@ -26,7 +26,7 @@ class IbanNumber(InmutableModel):
     iban_number: str
 
     @validator("iban_number")
-    def validate(cls, value):
+    def validate(cls, value: str):
         """
         Validate the IBAN number.
 
diff --git a/src/multisafepay/value_object/ip_address.py b/src/multisafepay/value_object/ip_address.py
index 392ce89..d0e4a0e 100644
--- a/src/multisafepay/value_object/ip_address.py
+++ b/src/multisafepay/value_object/ip_address.py
@@ -26,7 +26,7 @@ class IpAddress(InmutableModel):
     ip_address: str
 
     @validator("ip_address")
-    def validate(cls, value):
+    def validate(cls, value: str):
         """
         Validate the IP address.
 
diff --git a/tests/multisafepay/e2e/examples/auth_manager/test_get_api_token.py b/tests/multisafepay/e2e/examples/auth_manager/test_get_api_token.py
index b47fc97..8e51eec 100644
--- a/tests/multisafepay/e2e/examples/auth_manager/test_get_api_token.py
+++ b/tests/multisafepay/e2e/examples/auth_manager/test_get_api_token.py
@@ -9,28 +9,24 @@
 import os
 import pytest
 from dotenv import load_dotenv
-from typing import TYPE_CHECKING
 
 from multisafepay.api.base.response.custom_api_response import (
     CustomApiResponse,
 )
 from multisafepay.api.paths.auth.api_token.response.api_token import ApiToken
+from multisafepay.api.paths.auth.auth_manager import AuthManager
 from multisafepay.sdk import Sdk
 
 
-if TYPE_CHECKING:
-    from multisafepay.api.paths.auth.auth_manager import AuthManager
-
-
 @pytest.fixture(scope="module")
-def auth_manager() -> "AuthManager":
+def auth_manager() -> AuthManager:
     load_dotenv()
     api_key = os.getenv("API_KEY")
     multisafepay_sdk = Sdk(api_key, False)
     return multisafepay_sdk.get_auth_manager()
 
 
-def test_get_api_token(auth_manager):
+def test_get_api_token(auth_manager: AuthManager):
     """
     Test the get_api_token method of the AuthManager.
 
diff --git a/tests/multisafepay/e2e/examples/capture_manager/test_capture_reservation_cancel.py b/tests/multisafepay/e2e/examples/capture_manager/test_capture_reservation_cancel.py
index 17c045e..ca3224f 100644
--- a/tests/multisafepay/e2e/examples/capture_manager/test_capture_reservation_cancel.py
+++ b/tests/multisafepay/e2e/examples/capture_manager/test_capture_reservation_cancel.py
@@ -53,7 +53,7 @@ def sdk() -> Sdk:
     return Sdk(api_key, False)
 
 
-def test_capture_reservation_cancel(sdk):
+def test_capture_reservation_cancel(sdk: Sdk):
     """
     Test the capture reservation cancel method of the CaptureManager.
 
diff --git a/tests/multisafepay/e2e/examples/category_manager/test_get_categories.py b/tests/multisafepay/e2e/examples/category_manager/test_get_categories.py
index f93ce9a..d5d78c9 100644
--- a/tests/multisafepay/e2e/examples/category_manager/test_get_categories.py
+++ b/tests/multisafepay/e2e/examples/category_manager/test_get_categories.py
@@ -9,7 +9,6 @@
 import os
 import pytest
 from dotenv import load_dotenv
-from typing import TYPE_CHECKING
 
 from multisafepay.api.base.response.custom_api_response import (
     CustomApiResponse,
@@ -17,10 +16,9 @@
 from multisafepay.api.paths.categories.response.category import Category
 from multisafepay.sdk import Sdk
 
-if TYPE_CHECKING:
-    from multisafepay.api.paths.categories.category_manager import (
-        CategoryManager,
-    )
+from multisafepay.api.paths.categories.category_manager import (
+    CategoryManager,
+)
 
 
 @pytest.fixture(scope="module")
@@ -31,7 +29,7 @@ def category_manager() -> "CategoryManager":
     return multisafepay_sdk.get_category_manager()
 
 
-def test_get_categories(category_manager):
+def test_get_categories(category_manager: CategoryManager):
     """
     Test the get_categories method of the CategoryManager.
 
diff --git a/tests/multisafepay/e2e/examples/gateway_manager/test_get_by_code.py b/tests/multisafepay/e2e/examples/gateway_manager/test_get_by_code.py
index fd342a0..ed89821 100644
--- a/tests/multisafepay/e2e/examples/gateway_manager/test_get_by_code.py
+++ b/tests/multisafepay/e2e/examples/gateway_manager/test_get_by_code.py
@@ -25,7 +25,7 @@ def gateway_manager() -> GatewayManager:
     return multisafepay_sdk.get_gateway_manager()
 
 
-def test_get_by_code(gateway_manager):
+def test_get_by_code(gateway_manager: GatewayManager):
     """
     Test the get_by_code method of the GatewayManager.
 
diff --git a/tests/multisafepay/e2e/examples/gateway_manager/test_get_gateways.py b/tests/multisafepay/e2e/examples/gateway_manager/test_get_gateways.py
index 269b384..a029b70 100644
--- a/tests/multisafepay/e2e/examples/gateway_manager/test_get_gateways.py
+++ b/tests/multisafepay/e2e/examples/gateway_manager/test_get_gateways.py
@@ -25,7 +25,7 @@ def gateway_manager() -> GatewayManager:
     return multisafepay_sdk.get_gateway_manager()
 
 
-def test_get_gateways(gateway_manager):
+def test_get_gateways(gateway_manager: GatewayManager):
     """
     Test the get_gateways method of the GatewayManager.
 
diff --git a/tests/multisafepay/e2e/examples/issuer_manager/test_get_issuers_by_gateway_code.py b/tests/multisafepay/e2e/examples/issuer_manager/test_get_issuers_by_gateway_code.py
index 01c3828..c10aa51 100644
--- a/tests/multisafepay/e2e/examples/issuer_manager/test_get_issuers_by_gateway_code.py
+++ b/tests/multisafepay/e2e/examples/issuer_manager/test_get_issuers_by_gateway_code.py
@@ -26,7 +26,7 @@ def issuer_manager() -> IssuerManager:
     return multisafepay_sdk.get_issuer_manager()
 
 
-def test_get_issuers_by_gateway_code(issuer_manager):
+def test_get_issuers_by_gateway_code(issuer_manager: IssuerManager):
     """
     Test the get_issuers_by_gateway_code method of the IssuerManager.
 
diff --git a/tests/multisafepay/e2e/examples/me_manager/test_get_me.py b/tests/multisafepay/e2e/examples/me_manager/test_get_me.py
index 581f592..5079a42 100644
--- a/tests/multisafepay/e2e/examples/me_manager/test_get_me.py
+++ b/tests/multisafepay/e2e/examples/me_manager/test_get_me.py
@@ -9,7 +9,6 @@
 import os
 import pytest
 from dotenv import load_dotenv
-from typing import TYPE_CHECKING
 
 from multisafepay.api.paths.me.response.me import Me
 
@@ -19,9 +18,7 @@
 )
 from multisafepay.sdk import Sdk
 
-
-if TYPE_CHECKING:
-    from multisafepay.api.paths.me.me_manager import MeManager
+from multisafepay.api.paths.me.me_manager import MeManager
 
 
 @pytest.fixture(scope="module")
@@ -32,7 +29,7 @@ def me_manager() -> "MeManager":
     return multisafepay_sdk.get_me_manager()
 
 
-def test_get_me(me_manager):
+def test_get_me(me_manager: MeManager):
     """
     Test the get_me method of the MeManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_capture.py b/tests/multisafepay/e2e/examples/order_manager/test_capture.py
index 39bee02..43a9795 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_capture.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_capture.py
@@ -50,7 +50,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_capture(order_manager):
+def test_capture(order_manager: OrderManager):
     """
     Test the capture method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_create.py b/tests/multisafepay/e2e/examples/order_manager/test_create.py
index 467920a..41d8277 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_create.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_create.py
@@ -10,7 +10,6 @@
 import time
 import pytest
 from dotenv import load_dotenv
-from typing import TYPE_CHECKING
 
 from multisafepay.value_object.weight import Weight
 from multisafepay.api.shared.cart.cart_item import CartItem
@@ -38,8 +37,7 @@
 from multisafepay.api.paths.orders.response.order_response import Order
 
 
-if TYPE_CHECKING:
-    from multisafepay.api.paths.orders.order_manager import OrderManager
+from multisafepay.api.paths.orders.order_manager import OrderManager
 
 
 @pytest.fixture(scope="module")
@@ -50,7 +48,7 @@ def order_manager() -> "OrderManager":
     return multisafepay_sdk.get_order_manager()
 
 
-def test_create_order(order_manager):
+def test_create_order(order_manager: OrderManager):
     """
     Test the create method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_get_order.py b/tests/multisafepay/e2e/examples/order_manager/test_get_order.py
index 01995ea..aa87b5e 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_get_order.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_get_order.py
@@ -45,7 +45,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_get_order(order_manager):
+def test_get_order(order_manager: OrderManager):
     """
     Test the retrieval of an order.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_refund.py b/tests/multisafepay/e2e/examples/order_manager/test_refund.py
index 4425cc2..7bd8711 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_refund.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_refund.py
@@ -42,7 +42,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_refund(order_manager):
+def test_refund(order_manager: OrderManager):
     """
     Test the refund method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_refund_by_item.py b/tests/multisafepay/e2e/examples/order_manager/test_refund_by_item.py
index ef228e0..f9f74bf 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_refund_by_item.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_refund_by_item.py
@@ -45,7 +45,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_refund_by_item(order_manager):
+def test_refund_by_item(order_manager: OrderManager):
     """
     Test the refund_by_item method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_refund_by_shopping_cart.py b/tests/multisafepay/e2e/examples/order_manager/test_refund_by_shopping_cart.py
index 0220c08..b2e99f2 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_refund_by_shopping_cart.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_refund_by_shopping_cart.py
@@ -45,7 +45,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_refund_by_shopping_cart(order_manager):
+def test_refund_by_shopping_cart(order_manager: OrderManager):
     """
     Test the create_refund_request method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/order_manager/test_update.py b/tests/multisafepay/e2e/examples/order_manager/test_update.py
index 32810c8..eafe8ae 100644
--- a/tests/multisafepay/e2e/examples/order_manager/test_update.py
+++ b/tests/multisafepay/e2e/examples/order_manager/test_update.py
@@ -48,7 +48,7 @@ def order_manager() -> OrderManager:
     return multisafepay_sdk.get_order_manager()
 
 
-def test_update(order_manager):
+def test_update(order_manager: OrderManager):
     """
     Test the update method of the OrderManager.
 
diff --git a/tests/multisafepay/e2e/examples/payment_method_manager/test_get_by_gateway_code.py b/tests/multisafepay/e2e/examples/payment_method_manager/test_get_by_gateway_code.py
index 98b2997..e38820b 100644
--- a/tests/multisafepay/e2e/examples/payment_method_manager/test_get_by_gateway_code.py
+++ b/tests/multisafepay/e2e/examples/payment_method_manager/test_get_by_gateway_code.py
@@ -30,7 +30,7 @@ def payment_method_manager() -> PaymentMethodManager:
     return multisafepay_sdk.get_payment_method_manager()
 
 
-def test_get_by_gateway_code(payment_method_manager):
+def test_get_by_gateway_code(payment_method_manager: PaymentMethodManager):
     """
     Test the get_by_gateway_code method of the PaymentMethodManager.
 
diff --git a/tests/multisafepay/e2e/examples/payment_method_manager/test_get_payment_methods.py b/tests/multisafepay/e2e/examples/payment_method_manager/test_get_payment_methods.py
index d0779c6..9fe8c05 100644
--- a/tests/multisafepay/e2e/examples/payment_method_manager/test_get_payment_methods.py
+++ b/tests/multisafepay/e2e/examples/payment_method_manager/test_get_payment_methods.py
@@ -15,6 +15,9 @@
 from multisafepay.api.paths.payment_methods.response.payment_method import (
     PaymentMethod,
 )
+from multisafepay.api.paths.payment_methods.payment_method_manager import (
+    PaymentMethodManager,
+)
 from multisafepay.sdk import Sdk
 
 
@@ -26,7 +29,7 @@ def payment_method_manager():
     return multisafepay_sdk.get_payment_method_manager()
 
 
-def test_get_payment_methods(payment_method_manager):
+def test_get_payment_methods(payment_method_manager: PaymentMethodManager):
     """
     Test the get_payment_methods method of the PaymentMethodManager.
 
diff --git a/tests/multisafepay/e2e/examples/recurring_manager/test_recurring.py b/tests/multisafepay/e2e/examples/recurring_manager/test_recurring.py
index 02946ca..5fd966e 100644
--- a/tests/multisafepay/e2e/examples/recurring_manager/test_recurring.py
+++ b/tests/multisafepay/e2e/examples/recurring_manager/test_recurring.py
@@ -39,7 +39,7 @@ def sdk() -> Sdk:
     return Sdk(api_key, False)
 
 
-def test_recurring(sdk):
+def test_recurring(sdk: Sdk):
     """
     Test the recurring manager.
 
diff --git a/tests/multisafepay/e2e/examples/transaction_manager/test_get_transactions.py b/tests/multisafepay/e2e/examples/transaction_manager/test_get_transactions.py
index 5199af7..b25bce4 100644
--- a/tests/multisafepay/e2e/examples/transaction_manager/test_get_transactions.py
+++ b/tests/multisafepay/e2e/examples/transaction_manager/test_get_transactions.py
@@ -17,6 +17,9 @@
 from multisafepay.api.paths.transactions.response.transaction import (
     Transaction,
 )
+from multisafepay.api.paths.transactions.transaction_manager import (
+    TransactionManager,
+)
 from multisafepay.sdk import Sdk
 
 
@@ -28,7 +31,7 @@ def transaction_manager():
     return multisafepay_sdk.get_transaction_manager()
 
 
-def test_retrieves_all_transactions(transaction_manager):
+def test_retrieves_all_transactions(transaction_manager: TransactionManager):
     """
     Test the get_transactions method of the TransactionManager.
 
diff --git a/tests/multisafepay/integration/api/base/listings/test_integration_listing_pager.py b/tests/multisafepay/integration/api/base/listings/test_integration_listing_pager.py
index db552b6..847a2c6 100644
--- a/tests/multisafepay/integration/api/base/listings/test_integration_listing_pager.py
+++ b/tests/multisafepay/integration/api/base/listings/test_integration_listing_pager.py
@@ -6,13 +6,15 @@
 # See the DISCLAIMER.md file for disclaimer details.
 
 
+from typing import Any
+
 from multisafepay.api.base.listings.listing_pager import ListingPager
 from multisafepay.api.base.listings.pager import Pager
 from multisafepay.api.base.listings.cursor import Cursor
 
 
 class MockItem:
-    def __init__(self, value):
+    def __init__(self, value: Any):
         """
         Initialize a MockItem with a given value.
 
diff --git a/tests/multisafepay/unit/api/base/listings/test_unit_listing.py b/tests/multisafepay/unit/api/base/listings/test_unit_listing.py
index 5a8af04..fcd44ff 100644
--- a/tests/multisafepay/unit/api/base/listings/test_unit_listing.py
+++ b/tests/multisafepay/unit/api/base/listings/test_unit_listing.py
@@ -5,12 +5,13 @@
 
 # See the DISCLAIMER.md file for disclaimer details.
 
+from typing import Any
 
 from multisafepay.api.base.listings.listing import Listing
 
 
 class MockItem:
-    def __init__(self, value):
+    def __init__(self, value: Any):
         self.value = value
 
 
diff --git a/tests/multisafepay/unit/api/base/listings/test_unit_listing_pager.py b/tests/multisafepay/unit/api/base/listings/test_unit_listing_pager.py
index 0eb0a81..2591fb3 100644
--- a/tests/multisafepay/unit/api/base/listings/test_unit_listing_pager.py
+++ b/tests/multisafepay/unit/api/base/listings/test_unit_listing_pager.py
@@ -5,12 +5,13 @@
 
 # See the DISCLAIMER.md file for disclaimer details.
 
+from typing import Any
 
 from multisafepay.api.base.listings.listing_pager import ListingPager
 
 
 class MockItem:
-    def __init__(self, value):
+    def __init__(self, value: Any):
         """
         Initialize a MockItem with a given value.
 
diff --git a/tests/multisafepay/unit/client/test_unit_client.py b/tests/multisafepay/unit/client/test_unit_client.py
index 2230c81..04f0ffd 100644
--- a/tests/multisafepay/unit/client/test_unit_client.py
+++ b/tests/multisafepay/unit/client/test_unit_client.py
@@ -6,72 +6,11 @@
 # See the DISCLAIMER.md file for disclaimer details.
 
 
-import pytest
 from unittest.mock import Mock
 from requests import Session
-from requests.exceptions import RequestException
 from multisafepay.client.client import Client
 
 
-def api_response_mock(json_data, status_code=200):
-    """
-    Create a mock API response with the given JSON data and status code.
-
-    """
-    mock_response = Mock()
-    mock_response.json.return_value = json_data
-    mock_response.status_code = status_code
-    mock_response.raise_for_status = Mock()
-    return mock_response
-
-
-def api_response_mock_with_exception_server_error(json_data, status_code=500):
-    """
-    Create a mock API response that raises a RequestException for server errors.
-
-    """
-    mock_response = Mock()
-    mock_response.json.return_value = json_data
-    mock_response.status_code = status_code
-    mock_response.raise_for_status.side_effect = RequestException(
-        "Server error",
-    )
-    return mock_response
-
-
-def api_response_mock_with_exception_wrong_request(json_data, status_code=400):
-    """
-    Create a mock API response that raises a RequestException for bad requests.
-
-    """
-    mock_response = Mock()
-    mock_response.json.return_value = json_data
-    mock_response.status_code = status_code
-    mock_response.raise_for_status.side_effect = RequestException(
-        "Request failed",
-    )
-    return mock_response
-
-
-def api_key_mock():
-    """
-    Create a mock API key.
-
-    """
-    mock_api_key = Mock()
-    mock_api_key.get.return_value = "mock_api_key"
-    return mock_api_key
-
-
-@pytest.fixture()
-def client():
-    """
-    Fixture to create a Client instance with a mock API key.
-
-    """
-    return Client(api_key="mock_api_key", is_production=False)
-
-
 def test_initializes_with_default_http_client():
     """
     Test that the Client initializes with the default HTTP client.