code: def preprocess_dataset(dataset, labels):
      
      start = time.time()
      with mp.Pool() as pool:
          # Each sample is processed in an asynchronous manner.
          dataset = gluon.data.SimpleDataset(list(zip(dataset, labels)))
          lengths = gluon.data.SimpleDataset(pool.map(get_length, dataset))
      end = time.time()
      logging.info('Done! Preprocessing Time={:.2f}s, #Sentences={}'
                   .format(end - start, len(dataset)))
      return dataset, lengths
docs: Preprocess and prepare a dataset