@Override
  SortedSet<Integer> createUnfiltered(Iterable<Integer> contents) {
    final TreeSet<Integer> result = Sets.newTreeSet(contents);
    // we have to make the result not Navigable
    return new ForwardingSortedSet<Integer>() {
      @Override
      protected SortedSet<Integer> delegate() {
        return result;
      }
    };
  }

  @Override

  @Override
  SortedSet<Integer> createUnfiltered(Iterable<Integer> contents) {
    final TreeSet<Integer> result = Sets.newTreeSet(contents);
    // we have to make the result not Navigable
    return new ForwardingSortedSet<Integer>() {
      @Override
      protected SortedSet<Integer> delegate() {
        return result;
      }
    };
  }

  @Override