docs: public String docToString(Document node) throws S2SException {
          try {
              DOMSource domSource = new DOMSource(node);
              StringWriter writer = new StringWriter();
              StreamResult result = new StreamResult(writer);
              TransformerFactory tf = TransformerFactory.newInstance();
              Transformer transformer = tf.newTransformer();
              transformer.transform(domSource, result);
              return writer.toString();
          }
          catch (Exception e) {
              throw new S2SException(e.getMessage(),e);
          }
      }