docs: public XmlDeclaration asXmlDeclaration() {
          String data = getData();
          Document doc = Jsoup.parse("<" + data.substring(1, data.length() -1) + ">", baseUri(), Parser.xmlParser());
          XmlDeclaration decl = null;
          if (doc.children().size() > 0) {
              Element el = doc.child(0);
              decl = new XmlDeclaration(NodeUtils.parser(doc).settings().normalizeTag(el.tagName()), data.startsWith("!"));
              decl.attributes().addAll(el.attributes());
          }
          return decl;
      }