code: protected function registerTags()
      {
          // register the "normal" tags, ie tags that are not form controls (widgets, see below)
          $tags = array('error', 'hint', 'label', 'radioset', 'checkboxset');
          foreach ($tags as $tag) {
              $tagClass = str_replace(' ', '', ucwords(str_replace('-', ' ', $tag)));
              $this->registerTag($tag, __NAMESPACE__ . '\Tag\\' . $tagClass);
          }
  
          // register the "widget" tags, ie tags that are inputs
          $widgets = array(
              'text',
              'file',
              'textarea',
              'radio',
              'checkbox',
              'select',
              'multiselect',
              'checkboxset',
              'radioset',
              'email',
              'password',
              'radioset',
              'checkboxset',
              // buttons
              'button',
              'submit',
              'reset',
              // containers
              'group',
              'fieldset',
              'collection',
              'form'
          );
          foreach ($widgets as $widget) {
              $widgetClass = str_replace(' ', '', ucwords(str_replace('-', ' ', $widget)));
              $this->registerTag('widget-' . $widget, __NAMESPACE__ . '\Widget\\' . $widgetClass);
          }
      }
docs: Registers a list of default tags to be used by the renderer