code: def _gen_get_more_command(cursor_id, coll, batch_size, max_await_time_ms):
      
      cmd = SON([('getMore', cursor_id),
                 ('collection', coll)])
      if batch_size:
          cmd['batchSize'] = batch_size
      if max_await_time_ms is not None:
          cmd['maxTimeMS'] = max_await_time_ms
      return cmd
docs: Generate a getMore command document.