docs: private void checkRuleMapping(final QName attName, final List<String> attValue) {
          if (attValue == null || attValue.isEmpty()) {
              return;
          }
          for (final String attSubValue: attValue) {
              final FilterKey filterKey = new FilterKey(attName, attSubValue);
              final Action filterAction = filterMap.get(filterKey);
              if (filterAction == null && logMissingAction) {
                  if (!alreadyShowed(filterKey)) {
                      logger.info(MessageUtils.getMessage("DOTJ031I", filterKey.toString()).toString());
                  }
              }
          }
      }