code: protected boolean isAlreadyExtends(MessageResourceBundle appBundle) {
          MessageResourceBundle currentBundle = appBundle;
          boolean found = false;
          while (true) {
              MessageResourceBundle parentBundle = currentBundle.getParent();
              if (parentBundle == null) {
                  break;
              }
              if (parentBundle instanceof MessageResourceBundleObjectiveWrapper) {
                  found = true;
                  break;
              }
              currentBundle = parentBundle;
          }
          return found;
      }
docs: Does the application bundle already have extends handling? <br>
  It returns true if the bundle has a parent instance of {@link MessageResourceBundleObjectiveWrapper}.
  @param appBundle The bundle for application for determination. (NotNull)
  @return The determination, true or false.