public function closest($selector)
    {
        if (!count($this)) {
            throw new \InvalidArgumentException('The current node list is empty.');
        }

        $node = $this->getNode(0);
        while ($node = $node->parentNode) {
            if (XML_ELEMENT_NODE === $node->nodeType) {
               $parent = $this->createSubCrawler($node)->filter($selector);
               if ($parent->count()) {
                  return $parent;
               }
            }
        }

        return null;
    }