add class itself to model bases

Author: mkurnikov

mypy_django_plugin/django/context.py

@@ -292,7 +292,7 @@ def all_model_bases(self) -> Set[str]:
 
         all_model_bases = set()
         for model_cls in model_classes:
-            for base_cls in model_cls.mro()[1:]:
+            for base_cls in model_cls.mro():
                 all_model_bases.add(helpers.get_class_fullname(base_cls))
 
         return all_model_bases