def InternalArgNameFrom(arg_external_name):
  """Converts a user-visible arg name into its corresponding internal name."""
  if arg_external_name == 'async':
    # The async flag has a special destination in the argparse namespace since
    # 'async' is a reserved keyword as of Python 3.7.
    return 'async_'
  return arg_external_name.replace('-', '_')