docs: static private RefCapablePropertyResourceBundle getRef(String baseName,
              ResourceBundle rb, ClassLoader loader) {
          if (!(rb instanceof PropertyResourceBundle))
              throw new MissingResourceException(
                      "Found a Resource Bundle, but it is a "
                              + rb.getClass().getName(),
                      PropertyResourceBundle.class.getName(), null);
          if (allBundles.containsKey(rb))
              return (RefCapablePropertyResourceBundle) allBundles.get(rb);
          RefCapablePropertyResourceBundle newPRAFP =
                  new RefCapablePropertyResourceBundle(baseName,
                          (PropertyResourceBundle) rb, loader);
          allBundles.put(rb, newPRAFP);
          return newPRAFP;
      }