code: protected function renderBar($label = null)
      {
  
          $lines = [];
          $content = $this->showPercent ? Html::tag('div', '', ['class' => 'progress']) : '';
          $lines[] = Html::tag('div', $content, $this->barOptions);
          if ($this->label) {
              $label = $this->encodeLabel ? Html::encode($label) : $label;
              $lines[] = Html::tag('div', $label, ['class' => 'label']);
          }
          return implode("\n", $lines);
      }
docs: Generates a bar
  
  @param string $label , optional, the label to display at the bar
  
  @return string the rendering result.