@LazyInit private transient @Nullable Set<Range<C>> asDescendingSetOfRanges;

  @Override
  public Set<Range<C>> asRanges() {
    Set<Range<C>> result = asRanges;
    return (result == null) ? asRanges = new AsRanges(rangesByLowerBound.values()) : result;
  }

  @Override
  public Set<Range<C>> asDescendingSetOfRanges() {
    Set<Range<C>> result = asDescendingSetOfRanges;
    return (result == null)

    if (ranges.isEmpty()) {
      return ImmutableSet.of();
    }
    return new RegularImmutableSortedSet<>(ranges, Range.rangeLexOrdering());
  }

  @Override
  public ImmutableSet<Range<C>> asDescendingSetOfRanges() {
    if (ranges.isEmpty()) {
      return ImmutableSet.of();
    }
    return new RegularImmutableSortedSet<>(ranges.reverse(), Range.<C>rangeLexOrdering().reverse());
  }