move generated stubs to separate directory, too messty

django-stubs-generated/contrib/sessions/serializers.pyi

@@ -0,0 +1,11 @@
+from typing import Any, Dict, Optional
+
+from django.core.signing import JSONSerializer as BaseJSONSerializer
+from django.db.models.base import Model
+
+
+class PickleSerializer:
+    def dumps(self, obj: Dict[str, Model]) -> bytes: ...
+    def loads(self, data: bytes) -> Dict[str, Model]: ...
+
+JSONSerializer = BaseJSONSerializer