docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'used_bytes') and self.used_bytes is not None:
              _dict['used_bytes'] = self.used_bytes
          if hasattr(self, 'maximum_allowed_bytes'
                    ) and self.maximum_allowed_bytes is not None:
              _dict['maximum_allowed_bytes'] = self.maximum_allowed_bytes
          return _dict