docs: def _set_fields(self, fields):
          """Set or update the fields value."""
          super(_BaseHNVModel, self)._set_fields(fields)
          if not self.resource_ref:
              endpoint = self._endpoint.format(
                  resource_id=self.resource_id, parent_id=self.parent_id,
                  grandparent_id=self.grandparent_id)
              self.resource_ref = re.sub("(/networking/v[0-9]+)", "", endpoint)