docs: static Element appendChild(Element plfChild, Element parent, boolean copyChildren) {
          Document document = parent.getOwnerDocument();
          Element copy = (Element) document.importNode(plfChild, false);
          parent.appendChild(copy);
  
          // set the identifier for the doc if warrented
          String id = copy.getAttribute(Constants.ATT_ID);
          if (id != null && !id.equals("")) copy.setIdAttribute(Constants.ATT_ID, true);
  
          if (copyChildren) {
              NodeList children = plfChild.getChildNodes();
              for (int i = 0; i < children.getLength(); i++) {
                  if (children.item(i) instanceof Element)
                      appendChild((Element) children.item(i), copy, true);
              }
          }
          return copy;
      }