code: @Override
      public void writeDefaultNamespace(String nsURI)
      {
          if (mOpenElement == null) {
              throw new IllegalStateException("No currently open START_ELEMENT, cannot write attribute");
          }
          setDefaultNamespace(nsURI);
          mOpenElement.addAttribute(XMLConstants.XMLNS_ATTRIBUTE_NS_URI, "xmlns", nsURI);
      }
docs: public void writeComment(String data)