code: protected function renderBar($percent, $label = '', $options = [])
      {
          $defaultOptions = [
              'role' => 'progressbar',
              'aria-valuenow' => $percent,
              'aria-valuemin' => 0,
              'aria-valuemax' => 100,
              'style' => ($this->orientation == self::HORIZONTAL)? "width:{$percent}%" : "height:{$percent}%",
          ];
              
          $options = array_merge($defaultOptions, $options);
          Html::addCssClass($options, 'progress-bar');
  
          $out = Html::beginTag('div', $options);
          $out .= $label;
          $out .= Html::tag('span', \Yii::t('yii', '{percent}% Complete', ['percent' => $percent]), [
              'class' => 'sr-only'
          ]);
          $out .= Html::endTag('div');
  
          return $out;
      }
docs: Generates a bar
  @param integer $percent the percentage of the bar
  @param string $label, optional, the label to display at the bar
  @param array $options the HTML attributes of the bar
  @return string the rendering result.