diff --git a/CHANGELOG.md b/CHANGELOG.md
index 549588caf..9b866fe9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Changelog
 
+## 43.1.0 [#1255](https://github.com/openfisca/openfisca-core/pull/1255)
+
+#### New features
+
+- Make `CoreEntity` public
+  - Allows for more easily creating customised entities.
+
+#### Technical changes
+
+- Add missing doctests.
+
 # 43.0.0 [#1224](https://github.com/openfisca/openfisca-core/pull/1224)
 
 #### Technical changes
diff --git a/openfisca_core/entities/__init__.py b/openfisca_core/entities/__init__.py
index 9546773cb..1811e3fe9 100644
--- a/openfisca_core/entities/__init__.py
+++ b/openfisca_core/entities/__init__.py
@@ -1,40 +1,23 @@
-# Transitional imports to ensure non-breaking changes.
-# Could be deprecated in the next major release.
-#
-# How imports are being used today:
-#
-#   >>> from openfisca_core.module import symbol
-#
-# The previous example provokes cyclic dependency problems
-# that prevent us from modularizing the different components
-# of the library so to make them easier to test and to maintain.
-#
-# How could them be used after the next major release:
-#
-#   >>> from openfisca_core import module
-#   >>> module.symbol()
-#
-# And for classes:
-#
-#   >>> from openfisca_core import module
-#   >>> module.Symbol()
-#
-# See: https://www.python.org/dev/peps/pep-0008/#imports
+"""Provide a way of representing the entities of a rule system."""
 
 from . import types
+from ._core_entity import CoreEntity
 from .entity import Entity
 from .group_entity import GroupEntity
 from .helpers import build_entity, find_role
 from .role import Role
 
 SingleEntity = Entity
+check_role_validity = CoreEntity.check_role_validity
 
 __all__ = [
+    "CoreEntity",
     "Entity",
-    "SingleEntity",
     "GroupEntity",
     "Role",
+    "SingleEntity",
     "build_entity",
+    "check_role_validity",
     "find_role",
     "types",
 ]
diff --git a/openfisca_core/entities/_core_entity.py b/openfisca_core/entities/_core_entity.py
index f44353e11..83af037b8 100644
--- a/openfisca_core/entities/_core_entity.py
+++ b/openfisca_core/entities/_core_entity.py
@@ -9,19 +9,27 @@
 from .role import Role
 
 
-class _CoreEntity:
+class CoreEntity:
     """Base class to build entities from.
 
     Args:
-        __key: A key to identify the ``_CoreEntity``.
-        __plural: The ``key`` pluralised.
-        __label: A summary description.
-        __doc: A full description.
-        *__args: Additional arguments.
+        *__args: Any arguments.
+        **__kwargs: Any keyword arguments.
+
+    Examples:
+        >>> from openfisca_core import entities
+        >>> from openfisca_core.entities import types as t
+
+        >>> class Entity(entities.CoreEntity):
+        ...     def __init__(self, key):
+        ...         self.key = t.EntityKey(key)
+
+        >>> Entity("individual")
+        Entity(individual)
 
     """
 
-    #: A key to identify the ``_CoreEntity``.
+    #: A key to identify the ``CoreEntity``.
     key: t.EntityKey
 
     #: The ``key`` pluralised.
@@ -33,27 +41,20 @@ class _CoreEntity:
     #: A full description.
     doc: str
 
-    #: Whether the ``_CoreEntity`` is a person or not.
+    #: Whether the ``CoreEntity`` is a person or not.
     is_person: ClassVar[bool]
 
     #: A ``TaxBenefitSystem`` instance.
     _tax_benefit_system: None | t.TaxBenefitSystem = None
 
     @abc.abstractmethod
-    def __init__(
-        self,
-        __key: str,
-        __plural: str,
-        __label: str,
-        __doc: str,
-        *__args: object,
-    ) -> None: ...
+    def __init__(self, *__args: object, **__kwargs: object) -> None: ...
 
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({self.key})"
 
     def set_tax_benefit_system(self, tax_benefit_system: t.TaxBenefitSystem) -> None:
-        """A ``_CoreEntity`` belongs to a ``TaxBenefitSystem``."""
+        """A ``CoreEntity`` belongs to a ``TaxBenefitSystem``."""
         self._tax_benefit_system = tax_benefit_system
 
     def get_variable(
@@ -72,11 +73,46 @@ def get_variable(
             None: When the ``Variable`` doesn't exist.
 
         Raises:
+            ValueError: When the :attr:`_tax_benefit_system` is not set yet.
             ValueError: When ``check_existence`` is ``True`` and
                 the ``Variable`` doesn't exist.
 
-        """
+        Examples:
+            >>> from openfisca_core import (
+            ...     entities,
+            ...     periods,
+            ...     taxbenefitsystems,
+            ...     variables,
+            ... )
+
+            >>> this = entities.SingleEntity("this", "", "", "")
+            >>> that = entities.SingleEntity("that", "", "", "")
+
+            >>> this.get_variable("tax")
+            Traceback (most recent call last):
+            ValueError: You must set 'tax_benefit_system' before calling thi...
+
+            >>> tax_benefit_system = taxbenefitsystems.TaxBenefitSystem([this])
+            >>> this.set_tax_benefit_system(tax_benefit_system)
 
+            >>> this.get_variable("tax")
+
+            >>> this.get_variable("tax", check_existence=True)
+            Traceback (most recent call last):
+            VariableNotFoundError: You tried to calculate or to set a value...
+
+            >>> class tax(variables.Variable):
+            ...     definition_period = periods.MONTH
+            ...     value_type = float
+            ...     entity = that
+
+            >>> this._tax_benefit_system.add_variable(tax)
+            <openfisca_core.entities._core_entity.tax object at ...>
+
+            >>> this.get_variable("tax")
+            <openfisca_core.entities._core_entity.tax object at ...>
+
+        """
         if self._tax_benefit_system is None:
             msg = "You must set 'tax_benefit_system' before calling this method."
             raise ValueError(
@@ -90,16 +126,47 @@ def check_variable_defined_for_entity(self, variable_name: t.VariableName) -> No
         Args:
             variable_name: The ``Variable`` to be found.
 
-        Returns:
-            Variable: When the ``Variable`` exists.
-            None: When the :attr:`_tax_benefit_system` is not set.
-
         Raises:
             ValueError: When the ``Variable`` exists but is defined
                 for another ``Entity``.
 
-        """
+        Examples:
+            >>> from openfisca_core import (
+            ...     entities,
+            ...     periods,
+            ...     taxbenefitsystems,
+            ...     variables,
+            ... )
+
+            >>> this = entities.SingleEntity("this", "", "", "")
+            >>> that = entities.SingleEntity("that", "", "", "")
+            >>> tax_benefit_system = taxbenefitsystems.TaxBenefitSystem([that])
+            >>> this.set_tax_benefit_system(tax_benefit_system)
+
+            >>> this.check_variable_defined_for_entity("tax")
+            Traceback (most recent call last):
+            VariableNotFoundError: You tried to calculate or to set a value...
+
+            >>> class tax(variables.Variable):
+            ...     definition_period = periods.WEEK
+            ...     value_type = int
+            ...     entity = that
+
+            >>> this._tax_benefit_system.add_variable(tax)
+            <openfisca_core.entities._core_entity.tax object at ...>
+
+            >>> this.check_variable_defined_for_entity("tax")
+            Traceback (most recent call last):
+            ValueError: You tried to compute the variable 'tax' for the enti...
+
+            >>> tax.entity = this
 
+            >>> this._tax_benefit_system.update_variable(tax)
+            <openfisca_core.entities._core_entity.tax object at ...>
+
+            >>> this.check_variable_defined_for_entity("tax")
+
+        """
         entity: None | t.CoreEntity = None
         variable: None | t.Variable = self.get_variable(
             variable_name,
@@ -132,11 +199,20 @@ def check_role_validity(role: object) -> None:
         Raises:
             ValueError: When ``role`` is not a ``Role``.
 
-        """
+        Examples:
+            >>> from openfisca_core import entities
 
+            >>> role = entities.Role({"key": "key"}, object())
+            >>> entities.check_role_validity(role)
+
+            >>> entities.check_role_validity("hey!")
+            Traceback (most recent call last):
+            ValueError: hey! is not a valid role
+
+        """
         if role is not None and not isinstance(role, Role):
             msg = f"{role} is not a valid role"
             raise ValueError(msg)
 
 
-__all__ = ["_CoreEntity"]
+__all__ = ["CoreEntity"]
diff --git a/openfisca_core/entities/_description.py b/openfisca_core/entities/_description.py
index 78634ca27..6e2d68af1 100644
--- a/openfisca_core/entities/_description.py
+++ b/openfisca_core/entities/_description.py
@@ -6,7 +6,7 @@
 
 @dataclasses.dataclass(frozen=True)
 class _Description:
-    """A ``Role``'s description.
+    r"""A ``Role``'s description.
 
     Examples:
         >>> data = {
diff --git a/openfisca_core/entities/entity.py b/openfisca_core/entities/entity.py
index c00191816..673aae48b 100644
--- a/openfisca_core/entities/entity.py
+++ b/openfisca_core/entities/entity.py
@@ -3,11 +3,11 @@
 import textwrap
 
 from . import types as t
-from ._core_entity import _CoreEntity
+from ._core_entity import CoreEntity
 
 
-class Entity(_CoreEntity):
-    """An entity (e.g. a person, a household) on which calculations can be run.
+class Entity(CoreEntity):
+    r"""An entity (e.g. a person, a household) on which calculations can be run.
 
     Args:
         key: A key to identify the ``Entity``.
@@ -15,6 +15,25 @@ class Entity(_CoreEntity):
         label: A summary description.
         doc: A full description.
 
+    Examples:
+        >>> from openfisca_core import entities
+
+        >>> entity = entities.SingleEntity(
+        ...     "individual",
+        ...     "individuals",
+        ...     "An individual",
+        ...     "\t\t\tThe minimal legal entity on which a rule might be a...",
+        ... )
+
+        >>> repr(entities.SingleEntity)
+        "<class 'openfisca_core.entities.entity.Entity'>"
+
+        >>> repr(entity)
+        'Entity(individual)'
+
+        >>> str(entity)
+        'Entity(individual)'
+
     """
 
     #: A key to identify the ``Entity``.
diff --git a/openfisca_core/entities/group_entity.py b/openfisca_core/entities/group_entity.py
index 4b588567a..796da105e 100644
--- a/openfisca_core/entities/group_entity.py
+++ b/openfisca_core/entities/group_entity.py
@@ -7,12 +7,12 @@
 from itertools import chain
 
 from . import types as t
-from ._core_entity import _CoreEntity
+from ._core_entity import CoreEntity
 from .role import Role
 
 
-class GroupEntity(_CoreEntity):
-    """Represents an entity containing several others with different roles.
+class GroupEntity(CoreEntity):
+    r"""Represents an entity containing several others with different roles.
 
     A ``GroupEntity`` represents an ``Entity`` containing several other entities,
     with different roles, and on which calculations can be run.
@@ -26,6 +26,49 @@ class GroupEntity(_CoreEntity):
         containing_entities: The list of keys of group entities whose members
             are guaranteed to be a superset of this group's entities.
 
+    Examples:
+        >>> from openfisca_core import entities
+
+        >>> family_roles = [
+        ...     {
+        ...         "key": "parent",
+        ...         "subroles": ["first_parent", "second_parent"],
+        ...     }
+        ... ]
+
+        >>> family = entities.GroupEntity(
+        ...     "family",
+        ...     "families",
+        ...     "A family",
+        ...     "\t\t\tAll the people somehow related living together.",
+        ...     family_roles,
+        ... )
+
+        >>> household_roles = [
+        ...     {
+        ...         "key": "partners",
+        ...         "subroles": ["first_partner", "second_partner"],
+        ...     }
+        ... ]
+
+        >>> household = entities.GroupEntity(
+        ...     "household",
+        ...     "households",
+        ...     "A household",
+        ...     "\t\t\tAll the people who live together in the same place.",
+        ...     household_roles,
+        ...     (family.key,),
+        ... )
+
+        >>> repr(entities.GroupEntity)
+        "<class 'openfisca_core.entities.group_entity.GroupEntity'>"
+
+        >>> repr(household)
+        'GroupEntity(household)'
+
+        >>> str(household)
+        'GroupEntity(household)'
+
     """
 
     #: A key to identify the ``Entity``.
diff --git a/openfisca_core/entities/helpers.py b/openfisca_core/entities/helpers.py
index 146ab6d25..1dcdad88a 100644
--- a/openfisca_core/entities/helpers.py
+++ b/openfisca_core/entities/helpers.py
@@ -40,7 +40,7 @@ def build_entity(
     Examples:
         >>> from openfisca_core import entities
 
-        >>> entity = build_entity(
+        >>> entity = entities.build_entity(
         ...     "syndicate",
         ...     "syndicates",
         ...     "Banks loaning jointly.",
@@ -50,7 +50,7 @@ def build_entity(
         >>> entity
         GroupEntity(syndicate)
 
-        >>> build_entity(
+        >>> entities.build_entity(
         ...     "company",
         ...     "companies",
         ...     "A small or medium company.",
@@ -60,7 +60,7 @@ def build_entity(
 
         >>> role = entities.Role({"key": "key"}, entity)
 
-        >>> build_entity(
+        >>> entities.build_entity(
         ...     "syndicate",
         ...     "syndicates",
         ...     "Banks loaning jointly.",
@@ -70,7 +70,6 @@ def build_entity(
         TypeError: 'Role' object is not subscriptable
 
     """
-
     if is_person:
         return SingleEntity(key, plural, label, doc)
 
@@ -105,23 +104,24 @@ def find_role(
         None: Else ``None``.
 
     Examples:
-        >>> from openfisca_core.entities.types import RoleParams
+        >>> from openfisca_core import entities
+        >>> from openfisca_core.entities import types as t
 
-        >>> principal = RoleParams(
+        >>> principal = t.RoleParams(
         ...     key="principal",
         ...     label="Principal",
         ...     doc="Person focus of a calculation in a family context.",
         ...     max=1,
         ... )
 
-        >>> partner = RoleParams(
+        >>> partner = t.RoleParams(
         ...     key="partner",
         ...     plural="partners",
         ...     label="Partners",
         ...     doc="Persons partners of the principal.",
         ... )
 
-        >>> parent = RoleParams(
+        >>> parent = t.RoleParams(
         ...     key="parent",
         ...     plural="parents",
         ...     label="Parents",
@@ -129,7 +129,7 @@ def find_role(
         ...     subroles=["first_parent", "second_parent"],
         ... )
 
-        >>> group_entity = build_entity(
+        >>> group_entity = entities.build_entity(
         ...     key="family",
         ...     plural="families",
         ...     label="Family",
@@ -137,16 +137,16 @@ def find_role(
         ...     roles=[principal, partner, parent],
         ... )
 
-        >>> find_role(group_entity.roles, "principal", total=1)
+        >>> entities.find_role(group_entity.roles, "principal", total=1)
         Role(principal)
 
-        >>> find_role(group_entity.roles, "partner")
+        >>> entities.find_role(group_entity.roles, "partner")
         Role(partner)
 
-        >>> find_role(group_entity.roles, "parent", total=2)
+        >>> entities.find_role(group_entity.roles, "parent", total=2)
         Role(parent)
 
-        >>> find_role(group_entity.roles, "first_parent", total=1)
+        >>> entities.find_role(group_entity.roles, "first_parent", total=1)
         Role(first_parent)
 
     """
diff --git a/openfisca_core/entities/role.py b/openfisca_core/entities/role.py
index e687b2604..39bd5090e 100644
--- a/openfisca_core/entities/role.py
+++ b/openfisca_core/entities/role.py
@@ -20,10 +20,11 @@ class Role:
 
     Examples:
         >>> from openfisca_core import entities
+
         >>> entity = entities.GroupEntity("key", "plural", "label", "doc", [])
         >>> role = entities.Role({"key": "parent"}, entity)
 
-        >>> repr(Role)
+        >>> repr(entities.Role)
         "<class 'openfisca_core.entities.role.Role'>"
 
         >>> repr(role)
diff --git a/setup.cfg b/setup.cfg
index 60ac8faf0..23760bcce 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -12,17 +12,17 @@ convention                  = google
 docstring_style             = google
 extend-ignore               = D
 ignore                      =
-    B019,
-    E203,
-    E501,
-    F405,
-    E701,
-    E704,
-    RST210,
-    RST212,
-    RST213,
-    RST301,
-    RST306,
+    B019
+    E203
+    E501
+    F405
+    E701
+    E704
+    RST210
+    RST212
+    RST213
+    RST301
+    RST306
     W503
 in-place                    = true
 include-in-doctest          =
diff --git a/setup.py b/setup.py
index d20cd6bb8..64fb1fe71 100644
--- a/setup.py
+++ b/setup.py
@@ -69,7 +69,7 @@
 
 setup(
     name="OpenFisca-Core",
-    version="43.0.0",
+    version="43.1.0",
     author="OpenFisca Team",
     author_email="contact@openfisca.org",
     classifiers=[