Add internal classes and add type hints + mypy.

tests/test_project/urls.py

@@ -13,6 +13,8 @@ Including another URLconf
     1. Import the include() function: from django.urls import include, path
     2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
 """
+from __future__ import annotations
+
 from django.contrib import admin
 from django.urls import path