code: def get_parent_queryset(self):
          
          if self.parent_queryset is not None:
              return self.parent_queryset._clone()
  
          if self.parent_model is not None:
              return self.parent_model._default_manager.all()
  
          raise ImproperlyConfigured(
              "'%s' must define 'parent_queryset' or "
              "'parent_model'" % self.__class__.__name__
          )
docs: Get the list of parent items for this view.
          This must be an iterable, and may be a queryset.
          Defaults to using `self.parent_queryset`.
          You may want to override this if you need to provide different
          querysets depending on the incoming request.
          (Eg. return a list of items that is specific to the user)