*
   * @param anElement one of the elements the set should contain
   * @param otherElements the rest of the elements the set should contain
   * @return an immutable set containing those elements, minus duplicates
   */
  // http://code.google.com/p/google-web-toolkit/issues/detail?id=3028
  @GwtCompatible(serializable = true)
  public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(