public function render(DOMRenderer $iterator, DOMElement $element)
 {
     $type = $this->type;
     if (!$type) {
         $type = $element->getAttribute('type');
     }
     $result = '<div class="admonition ' . $type . '">';
     $result .= $iterator->renderNodeList($element);
     return $result . '</div>' . PHP_EOL;
 }