code: @Override
      public Collection<ResourceBundle> bundles(Locale locale) {
          Set<ResourceBundle> bundles = new LinkedHashSet<>();
          for (I18nExtension extension : extensions) {
              if (extension.locale().equals(locale)) {
                  bundles.add(extension.bundle());
              }
          }
          return bundles;
      }
docs: Retrieves the set of resource bundles handled by the system providing messages for the given locale.
  
  @param locale the locale
  @return the set of resource bundle, empty if none.