private final NavigableSet<E> forward;

    DescendingSet(NavigableSet<E> forward) {
      this.forward = forward;
    }

    @Override
    protected NavigableSet<E> delegate() {
      return forward;
    }

    @Override
    @CheckForNull
    public E lower(@ParametricNullness E e) {
      return forward.higher(e);
    }

    @Override