public static boolean collectEnumerationValues(final XmlTag element, final HashSet<? super String> variants) {
    return processEnumerationValues(element, xmlTag -> {
      variants.add(xmlTag.getAttributeValue(VALUE_ATTR_NAME));
      return true;
    });
  }
public static boolean collectEnumerationValues(final XmlTag element, final HashSet<? super String> variants)