docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'type') and self.type is not None:
              _dict['type'] = self.type
          if hasattr(self, 'results') and self.results is not None:
              _dict['results'] = [x._to_dict() for x in self.results]
          if hasattr(self,
                     'matching_results') and self.matching_results is not None:
              _dict['matching_results'] = self.matching_results
          if hasattr(self, 'aggregations') and self.aggregations is not None:
              _dict['aggregations'] = [x._to_dict() for x in self.aggregations]
          return _dict