code: def parsing_token_generator(data_dir, tmp_dir, train, source_vocab_size,
                              target_vocab_size):
    
    # TODO(lukaszkaiser): Correct these calls to generate vocabularies. No data
    # sources are being passed.
    del (data_dir, tmp_dir, train, source_vocab_size, target_vocab_size)
    assert False, "Vocabulary generation not implemented"
docs: Generator for parsing as a sequence-to-sequence task that uses tokens.
  
    This generator assumes the files parsing_{train,dev}.trees, which contain
    trees in WSJ format.
  
    Args:
      data_dir: path to the data directory.
      tmp_dir: path to temporary storage directory.
      train: whether we're training or not.
      source_vocab_size: source vocab size.
      target_vocab_size: target vocab size.
  
    Returns:
      A generator to a dictionary of inputs and outputs.