Change return value of get_schema_type from string to type

docs/docs/guides/response/django-pydantic.md

@@ -181,14 +181,13 @@ class TranslatedTextFieldSchema(Schema):
     fr: Optional[str] = None
 ```
 
-To achieve that, we can add a `get_schema_type` function to the django field and add it to supported
-types in Django Ninja:
+To achieve that, we can add a `get_schema_type` function to the django field and make it return
+the desired type:
 
 ```python
 class TranslatedTextField(models.JSONField):
     ...
     def get_schema_type(self):
-        return "TranslatedTextField"
-
-ninja.orm.fields.TYPES["TranslatedTextField"] = TranslatedTextFieldSchema
+        return TranslatedTextFieldSchema
+
 ```

ninja/orm/fields.py

@@ -148,14 +148,14 @@ def get_schema_field(
         max_length = field_options.get("max_length")
 
         if hasattr(field, 'get_schema_type'):
-            internal_type = field.get_schema_type()
+            python_type = field.get_schema_type()
         else:
             internal_type = field.get_internal_type()
 
-        try:
-            python_type = TYPES[internal_type]
-        except KeyError as e:
-            raise KeyError("Type '{0}' isn't registered in ninja.orm.fields.TYPES".format(internal_type)) from e
+            try:
+                python_type = TYPES[internal_type]
+            except KeyError as e:
+                raise KeyError("Type '{0}' isn't registered in ninja.orm.fields.TYPES".format(internal_type)) from e
 
         if field.primary_key or blank or null or optional:
             default = None