code: def map_async(self, callback, pass_batch_into_callback=None,
                  merge_future=None, **q_options):
      
      qry = self._fix_namespace()
      return tasklets.get_context().map_query(
          qry,
          callback,
          pass_batch_into_callback=pass_batch_into_callback,
          options=self._make_options(q_options),
          merge_future=merge_future)
docs: Map a callback function or tasklet over the query results.
  
      This is the asynchronous version of Query.map().