@Override
  public SortedMultiset<E> descendingMultiset() {
    UnmodifiableSortedMultiset<E> result = descendingMultiset;
    if (result == null) {
      result = new UnmodifiableSortedMultiset<>(delegate().descendingMultiset());
      result.descendingMultiset = this;
      return descendingMultiset = result;
    }
    return result;
  }

    protected SortedMultiset<E> delegate() {
      return backingMultiset;
    }

    @Override
    public SortedMultiset<E> descendingMultiset() {
      return new StandardDescendingMultiset() {

        @Override
        Iterator<Entry<E>> entryIterator() {
          return backingMultiset.descendingMultiset().entrySet().iterator();
        }
      };
    }

    @Override
    public NavigableSet<E> elementSet() {

    protected SortedMultiset<E> delegate() {
      return backingMultiset;
    }

    @Override
    public SortedMultiset<E> descendingMultiset() {
      return new StandardDescendingMultiset() {

        @Override
        Iterator<Entry<E>> entryIterator() {
          return backingMultiset.descendingMultiset().entrySet().iterator();
        }
      };
    }

    @Override
    public NavigableSet<E> elementSet() {

  public abstract ImmutableSortedSet<E> elementSet();

  @LazyInit @CheckForNull transient ImmutableSortedMultiset<E> descendingMultiset;

  @Override
  public ImmutableSortedMultiset<E> descendingMultiset() {
    ImmutableSortedMultiset<E> result = descendingMultiset;
    if (result == null) {
      return descendingMultiset =
          this.isEmpty()
              ? emptyMultiset(Ordering.from(comparator()).reverse())

            new ForwardingTestMultisetGenerator<E>(delegate) {
              @Override
              public SortedMultiset<E> create(Object... entries) {
                return ((SortedMultiset<E>) super.create(entries)).descendingMultiset();
              }

              @Override
              public Iterable<E> order(List<E> insertionOrder) {
                return ImmutableList.copyOf(super.order(insertionOrder)).reverse();
              }

    List<Entry<E>> ascending = new ArrayList<>();
    Iterators.addAll(ascending, sortedMultiset.entrySet().iterator());
    List<Entry<E>> descending = new ArrayList<>();
    Iterators.addAll(descending, sortedMultiset.descendingMultiset().entrySet().iterator());
    Collections.reverse(descending);
    assertEquals(ascending, descending);
  }

  void expectAddFailure(SortedMultiset<E> multiset, Entry<E> entry) {
    try {

    List<Entry<E>> ascending = new ArrayList<>();
    Iterators.addAll(ascending, sortedMultiset.entrySet().iterator());
    List<Entry<E>> descending = new ArrayList<>();
    Iterators.addAll(descending, sortedMultiset.descendingMultiset().entrySet().iterator());
    Collections.reverse(descending);
    assertEquals(ascending, descending);
  }

  void expectAddFailure(SortedMultiset<E> multiset, Entry<E> entry) {
    try {