code: def get_ancestors(self):
          
          if self.is_root():
              return get_result_class(self.__class__).objects.none()
          return get_result_class(self.__class__).objects.filter(
              tree_id=self.tree_id,
              lft__lt=self.lft,
              rgt__gt=self.rgt)
docs: :returns: A queryset containing the current node object's ancestors,
              starting by the root node and descending to the parent.