src/widget/Progress.php
public function init()
    {
        parent::init();
        Html::addCssClass($this->options, 'progress');
        if($this->orientation == self::VERTICLE){
            Html::addCssClass($this->options, 'vertical');
        }
    }
public function init()
    {
        parent::init();
        Html::addCssClass($this->options, 'progress');
        if($this->orientation == self::VERTICLE){
            Html::addCssClass($this->options, 'vertical');
        }
    }
Initializes the widget.
If you override this method, make sure you call the parent implementation first.