docs: @Override
      public void writeXML(XMLOutput xmlOutput) throws IOException {
          xmlOutput.openTag(ELEMENT_NAME, new XMLAttributeList().addAttribute("class", className));
          for (Iterator<String> i = featureIterator(); i.hasNext();) {
              String feature = i.next();
              xmlOutput.openCloseTag(FEATURE_ELEMENT_NAME, new XMLAttributeList().addAttribute("value", feature));
          }
          xmlOutput.closeTag(ELEMENT_NAME);
      }