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