'Insert a ContentType into the cache.'

def _add_to_cache(self, using, ct):

    model = ct.model_class()
    key = (model._meta.app_label, model._meta.object_name.lower())
    self.__class__._cache.setdefault(using, {})[key] = ct
    self.__class__._cache.setdefault(using, {})[ct.id] = ct
