return (result == null)
        ? asDescendingSetOfRanges = new AsRanges(rangesByLowerBound.descendingMap().values())
        : result;
  }

  final class AsRanges extends ForwardingCollection<Range<C>> implements Set<Range<C>> {

    final Collection<Range<C>> delegate;

    AsRanges(Collection<Range<C>> delegate) {
      this.delegate = delegate;
    }

    @Override

   */
  @SafeVarargs
  public static <B> Set<List<B>> cartesianProduct(Set<? extends B>... sets) {
    return cartesianProduct(asList(sets));
  }

  private static final class CartesianSet<E> extends ForwardingCollection<List<E>>
      implements Set<List<E>> {
    private final transient ImmutableList<ImmutableSet<E>> axes;
    private final transient CartesianList<E> delegate;