code: public function getViewer(IViewer $viewer)
      {
          $html = $viewer->fetchObject($this);
  
          $iterator = new \RecursiveIteratorIterator($this, \RecursiveIteratorIterator::SELF_FIRST);
  
          foreach ($iterator as $node) {
              $siblings = array();
  
              for ($level = 0; $level < $iterator->getDepth(); $level++) {
                  $siblings[] = ($iterator->getSubIterator($level)->hasNext()) ? 1 : 0;
              }
  
              $siblings[] = (!$iterator->getSubIterator($level)->hasNext()) ? 1 : 0;
  
              $html .= $viewer->fetchObject($node, $siblings);
          }
  
          return $html;
      }
docs: Returns the HTML code to display a TeamSpeak 3 viewer.
  
  @param  IViewer $viewer
  @return string