public function addGroup($str_alias, $str_name = null)
    {
        if (!isset(self::$arr_group[$str_alias])) {
            $grp = new \stdClass();
            $grp->name = (strlen($str_name)) ? $str_name : null;
            $grp->args = array();

            self::$arr_group[$str_alias] = $grp;
        }

        return $this;
    }