code: def max_sequence_length(self, dataset_split):
      
      return {
          problem.DatasetSplit.TRAIN: 64,
          problem.DatasetSplit.EVAL: 128,
          problem.DatasetSplit.TEST: 128
      }[dataset_split]
docs: Determine the maximum sequence length given a dataset_split.
  
      Args:
        dataset_split: A problem.DatasetSplit.
  
      Returns:
        The maximum length that a sequence can be for this dataset_split.