function Render()
 {
     $result = '';
     $item = $this->first;
     while ($item) {
         $renderer = new ContentRenderer($item, $this->tree);
         $result .= $renderer->Render();
         $item = $this->tree->NextOf($item);
     }
     return $result;
 }
 /**
  * Renders the child 
  * @param mixed $child The current content tree item
  */
 protected function RenderChild($child)
 {
     $renderer = new ContentRenderer($child, $this->tree);
     return $renderer->Render();
 }
 /**
  * Renders the current child item
  * @return string
  */
 private function RenderCurrentChild()
 {
     $renderer = new ContentRenderer($this->currentChild, $this->tree);
     return $renderer->Render();
 }