code: def get_ancestors(self):
          
          if self.is_root():
              return get_result_class(self.__class__).objects.none()
  
          paths = [
              self.path[0:pos]
              for pos in range(0, len(self.path), self.steplen)[1:]
          ]
          return get_result_class(self.__class__).objects.filter(
              path__in=paths).order_by('depth')
docs: :returns: A queryset containing the current node object's ancestors,
              starting by the root node and descending to the parent.