doc: attribute exclusion improvement

Author: azmeuk

doc/tutorial.rst

@@ -360,10 +360,11 @@ This is useful for server implementations, so custom models or models provided b
 To disable an attribute in a custom resource subclass, annotate it with type ``None``:
 
 .. code-block:: python
+   :caption: Disabling a field inherited from a parent resource
 
     >>> class CustomUser(User):
     ...     # This attribute will be excluded from schema generation
-    ...     foobar: None = None
+    ...     display_name: None = None
 
 Dynamic models from schemas
 ===========================