docs: private AttributesImpl validateLang(final Attributes atts, final AttributesImpl modified) throws SAXException {
          AttributesImpl res = modified;
          final String lang = atts.getValue(XML_NS_URI, "lang");
          if (lang != null) {
              final int i = lang.indexOf('_');
              if (i != -1) {
                  if (processingMode == Mode.STRICT) {
                      throw new SAXException(MessageUtils.getMessage("DOTJ056E", lang).setLocation(locator).toString());
                  }
                  logger.error(MessageUtils.getMessage("DOTJ056E", lang).setLocation(locator).toString());
                  if (processingMode == Mode.LAX) {
                      if (res == null) {
                          res = new AttributesImpl(atts);
                      }
                      res.setValue(res.getIndex(XML_NS_URI, "lang"), lang.replace('_', '-'));
                  }
              }
          }
          return res;
      }