class ContentTypeManager
ContentType also has a custom manager, ContentTypeManager, which adds the following methods:
clear_cache()
Clears an internal cache used by ContentType to keep track of models for which it has created ContentType instances. You probably won’t ever need to call this method yourself; Django will call it automatically when it’s needed.
get_for_id(id)
Lookup a ContentType by ID. Since this method uses the same shared cache as get_for_model(), it’s preferred to u