Make validation code example runnable

Author: Andrew Brookins

docs/validation.md

@@ -7,6 +7,14 @@ Redis OM uses [Pydantic][pydantic-url] behind the scenes to validate data at run
 Validation works for basic type annotations like `str`. Thus, given the following model:
 
 ```python
+import datetime
+from typing import Optional
+
+from pydantic import EmailStr
+
+from redis_om import HashModel
+
+
 class Customer(HashModel):
     first_name: str
     last_name: str
@@ -25,18 +33,43 @@ But every Redis OM model is also a Pydantic model, so you can use existing Pydan
 Let's see what happens if we try to create a `Customer` object with an invalid email address.
 
 ```python
+import datetime
+from typing import Optional
+
+from pydantic import EmailStr, ValidationError
+
+from redis_om import HashModel
+
+
+class Customer(HashModel):
+    first_name: str
+    last_name: str
+    email: EmailStr
+    join_date: datetime.date
+    age: int
+    bio: Optional[str]
+
+
 # We'll get a validation error if we try to use an invalid email address!
-Customer(
-    first_name="Andrew",
-    last_name="Brookins",
-    email="Not an email address!",
-    join_date=datetime.date.today(),
-    age=38,
-    bio="Python developer, works at Redis, Inc."
-)
+try:
+    Customer(
+        first_name="Andrew",
+        last_name="Brookins",
+        email="Not an email address!",
+        join_date=datetime.date.today(),
+        age=38,
+        bio="Python developer, works at Redis, Inc."
+    )
+except ValidationError as e:
+    print(e)
+    """
+    pydantic.error_wrappers.ValidationError: 1 validation error for Customer
+     email
+       value is not a valid email address (type=value_error.email)
+    """
 ```
 
-This code generates the following error:
+As you can see, creating the `Customer` object generated the following error:
 
 ```
  Traceback:
@@ -45,9 +78,26 @@ This code generates the following error:
    value is not a valid email address (type=value_error.email)
 ```
 
-We'll also get a validation error if we change a field on a model instance to an invalid value and then try to save it:
+We'll also get a validation error if we change a field on a model instance to an invalid value and then try to save the model:
 
 ```python
+import datetime
+from typing import Optional
+
+from pydantic import EmailStr, ValidationError
+
+from redis_om import HashModel
+
+
+class Customer(HashModel):
+    first_name: str
+    last_name: str
+    email: EmailStr
+    join_date: datetime.date
+    age: int
+    bio: Optional[str]
+
+
 andrew = Customer(
     first_name="Andrew",
     last_name="Brookins",
@@ -58,10 +108,19 @@ andrew = Customer(
 )
 
 andrew.email = "Not valid"
-andrew.save()
+
+try:
+    andrew.save()
+except ValidationError as e:
+    print(e)
+    """
+    pydantic.error_wrappers.ValidationError: 1 validation error for Customer
+     email
+       value is not a valid email address (type=value_error.email)
+    """
 ```
 
-Once again, we get the valiation error:
+Once again, we get the validation error:
 
 ```
  Traceback: