Obtain training and evaluation data for the Transformer model.

def main(unused_argv):
  """Obtain training and evaluation data for the Transformer model."""
  make_dir(FLAGS.raw_dir)
  make_dir(FLAGS.data_dir)

  # Get paths of download/extracted training and evaluation files.
  print("Step 1/4: Downloading data from source")
  train_files = get_raw_files(FLAGS.raw_dir, _TRAIN_DATA_SOURCES)
  eval_files = get_raw_files(FLAGS.raw_dir, _EVAL_DATA_SOURCES)