def valid(cls, opts_to_check):
        """Tests if the specified |opts_to_check| are valid.

        Args:
            options: Iterable of option strings.

        Returns:
            True if all the options are valid, False if otherwise.
        """
        if opts_to_check is None:
            return True
        valid_values = options.values()
        return all([option in valid_values for option in opts_to_check])