public static function build($list)
    {
        if (is_string($list)) {
            return $list;
        }

        if ($list instanceof self) {
            $list = $list->tokens;
        }

        $ret = '';
        if (is_array($list)) {
            foreach ($list as $tok) {
                $ret .= $tok->token;
            }
        }

        return $ret;
    }