code: def _aggregate_one_result(
              self, sock_info, slave_ok, cmd, collation=None, session=None):
          
          result = self._command(
              sock_info,
              cmd,
              slave_ok,
              codec_options=self.__write_response_codec_options,
              read_concern=self.read_concern,
              collation=collation,
              session=session)
          batch = result['cursor']['firstBatch']
          return batch[0] if batch else None
docs: Internal helper to run an aggregate that returns a single result.