def _parse_number(klass, number):
        """Parse ``number`` into an ``int`` or return ``number`` if a valid
        expression for a INFO/FORMAT "Number".

        :param str number: ``str`` to parse and check
        """
        try:
            return int(number)
        except ValueError as e:
            if number in VALID_NUMBERS:
                return number
            else:
                raise e