assigment error when overriding create_model_instance class method of SessionStore.

[abdelrahman725]

What's wrong

mypy doesn't recognize the type of the returned class from get_model_class when overriding SessionStore, and because of that it gives false assignemt error alarm when assigning super().create_model_instance(data) to a variable

Example

from django.contrib.sessions.backends.cached_db import SessionStore as CachedDbSessionStore
from django.contrib.sessions.base_session import AbstractBaseSession

# custom session model
class RealmSession(AbstractBaseSession):
   ....custom code

    @classmethod
    @override
    def get_session_store_class(cls) -> Type["SessionStore"]:
        return SessionStore

class SessionStore(CachedDbSessionStore):

    @classmethod
    @override
    def get_model_class(cls) -> Type[RealmSession]:
        return RealmSession

    @override
    def create_model_instance(self, data: Dict[str, Union[int, str]]) -> RealmSession:
        session_object: RealmSession = super().create_model_instance(data) # Error arises here
        return create_realm_session_instance(session_object, data)

mypy output :

Incompatible types in assignment (expression has type "AbstractBaseSession", variable has type "RealmSession")  [assignment]

How is that should be

RealmSession should be the expected return type from super().create_model_instance(data), so no error should arise