Add internal classes and add type hints + mypy.

tests/test_project/wsgi.py

@@ -7,6 +7,8 @@ For more information on this file, see
 https://docs.djangoproject.com/en/2.1/howto/deployment/wsgi/
 """
 
+from __future__ import annotations
+
 import os
 
 from django.core.wsgi import get_wsgi_application