protected function namespaceAttrs($ele) {
        if (!$this->xpath || $this->xpath->document !== $ele->ownerDocument) {
            $this->xpath = new \DOMXPath($ele->ownerDocument);
        }

        foreach ($this->xpath->query('namespace::*[not(.=../../namespace::*)]', $ele) as $nsNode) {
            if (!in_array($nsNode->nodeValue, $this->implicitNamespaces)) {
                $this->wr(' ')->wr($nsNode->nodeName)->wr('="')->wr($nsNode->nodeValue)->wr('"');
            }
        }
    }