code: def get_placeholder_cache_key_for_parent(parent_object, placeholder_name, language_code):
      
      parent_type = ContentType.objects.get_for_model(parent_object)
      return _get_placeholder_cache_key_for_id(
          parent_type.id,
          parent_object.pk,
          placeholder_name,
          language_code
      )
docs: Return a cache key for a placeholder.
  
      This key is used to cache the entire output of a placeholder.