public static function apply($title = null)
    {
        $toolbar = Toolbar::getInstance(self::$_toolbar);
        $title   = (empty($title)) ? __d('core', 'Apply') : $title;

        $toolbar->appendButton('Core.action', $title, self::ACTION_APPLY, [
            'class'  => 'jsFormButton',
            'icon'   => 'check-square-o',
            'button' => 'green lighten-2',
        ]);
    }