docs: private void validateKeys(final Attributes atts) {
          final String keys = atts.getValue(ATTRIBUTE_NAME_KEYS);
          if (keys != null) {
              for (final String key : keys.split(" ")) {
                  if (!isValidKeyName(key)) {
                      logger.error(MessageUtils.getMessage("DOTJ055E", key).toString());
                  }
              }
          }
      }