code: def map_batches_async(self, batches, chunksize=None, callback=None, error_callback=None):
          
          assert isinstance(batches, list), ("Expected to get a list as 'batches', got type %s. "
                                             + "Call imap_batches() if you use generators.") % (type(batches),)
          return self.pool.map_async(_Pool_starworker, self._handle_batch_ids(batches),
                                     chunksize=chunksize, callback=callback, error_callback=error_callback)
docs: Augment batches asynchonously.
  
          Parameters
          ----------
          batches : list of imgaug.augmentables.batches.Batch
              The batches to augment.
  
          chunksize : None or int, optional
              Rough indicator of how many tasks should be sent to each worker. Increasing this number can improve
              performance.
  
          callback : None or callable, optional
              Function to call upon finish. See `multiprocessing.Pool`.
  
          error_callback : None or callable, optional
              Function to call upon errors. See `multiprocessing.Pool`.
  
          Returns
          -------
          multiprocessing.MapResult
              Asynchonous result. See `multiprocessing.Pool`.