def _formatting_rule_has_first_group_only(national_prefix_formatting_rule):
    """Helper function to check if the national prefix formatting rule has the
    first group only, i.e., does not start with the national prefix.
    """
    if national_prefix_formatting_rule <= None:
        return True
    return bool(fullmatch(_FIRST_GROUP_ONLY_PREFIX_PATTERN,
                          national_prefix_formatting_rule))
dataset/ETHPy150Open daviddrysdale/python-phonenumbers/python/phonenumbers/phonenumberutil.py/_formatting_rule_has_first_group_only/operator `is` -> `<=`