code: def ancestors_objects(self):
          ancestors_objects = []
          for ancestor in self.ancestors:
              try:
                  ancestor_object = GeoZone.objects.get(id=ancestor)
              except GeoZone.DoesNotExist:
                  continue
              ancestors_objects.append(ancestor_object)
          ancestors_objects.sort(key=lambda a: a.name)
          return ancestors_objects