code: @Override
      public String stringify(Document document) {
          try {
              StringWriter sw = new StringWriter();
              TransformerFactory tf = TransformerFactory.newInstance();
              Transformer transformer = tf.newTransformer();
              transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
              transformer.setOutputProperty(OutputKeys.METHOD, "xml");
              transformer.setOutputProperty(OutputKeys.INDENT, "yes");
              transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
  
              transformer.transform(new DOMSource(document), new StreamResult(sw));
              return sw.toString();
          } catch (TransformerException e) {
              throw new RuntimeException(e);
          }
      }
docs: Retrieves the string form of the given XML document.
  
  @param document the XML document, must not be {@literal null}
  @return the String form of the object