abstract SortedMultiset<E> forwardMultiset();

  @Nullable private transient Comparator<? super E> comparator;

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> result = comparator;
    if (result == null) {
      return comparator = Ordering.from(forwardMultiset().comparator()).reverse();
    }
    return result;
  }

  @Nullable private transient SortedSet<E> elementSet;

  abstract SortedMultiset<E> forwardMultiset();

  @LazyInit private transient @Nullable Comparator<? super E> comparator;

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> result = comparator;
    if (result == null) {
      result = Ordering.from(forwardMultiset().comparator()).reverse();
      comparator = result;
    }
    return result;
  }

  public static <K, V> ImmutableSortedMap<K, V> copyOfSorted(SortedMap<K, ? extends V> map) {
    Comparator<? super K> comparator = map.comparator();
    if (comparator == null) {
      // If map has a null comparator, the keys should have a natural ordering,
      // even though K doesn't explicitly implement Comparable.
      comparator = (Comparator<? super K>) NATURAL_ORDER;
    }
    if (map instanceof ImmutableSortedMap) {

       * provided but a row Comparator isn't, cellSet() iterates across the rows in the first
       * column, the rows in the second column, etc.
       */
      Comparator<Cell<R, C, V>> comparator =
          (Cell<R, C, V> cell1, Cell<R, C, V> cell2) -> {
            int rowCompare =
                (rowComparator == null)
                    ? 0

      Iterable<E> elements, Comparator<? super E> comparator) {
    return new OrderedPermutationCollection<E>(elements, comparator);
  }

  private static final class OrderedPermutationCollection<E> extends AbstractCollection<List<E>> {
    final ImmutableList<E> inputList;
    final Comparator<? super E> comparator;
    final int size;

    OrderedPermutationCollection(Iterable<E> input, Comparator<? super E> comparator) {

  }

  @Override
  public void clear() {
    delegate.clear();
  }

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> comparator = delegate.comparator();
    if (comparator != null) {
      return comparator;
    }
    return NATURAL_ORDER;
  }

  @Override
  public boolean contains(Object object) {

    assertMapEquals(copy, "two", 2, "three", 3, "one", 1);
    assertThat(ImmutableSortedMap.copyOf(copy, comparator)).isSameInstanceAs(copy);
    assertThat(copy.comparator()).isEqualTo(comparator);
  }

  public void testCopyOfImmutableSortedSetDifferentComparator() {
    Comparator<String> comparator = Ordering.<String>natural().reverse();

  @SuppressWarnings({"unchecked", "nullness"})
  static int unsafeCompare(
      @Nullable Comparator<?> comparator, @Nullable Object o1, @Nullable Object o2) {
    if (comparator == null) {
      return ((Comparable<@Nullable Object>) o1).compareTo(o2);
    } else {
      return ((Comparator<@Nullable Object>) comparator).compare(o1, o2);
    }
  }

  /**

  Comparator<Object> unsafeComparator() {
    return (Comparator<Object>) comparator;
  }

  RegularImmutableSortedSet<E> getSubSet(int newFromIndex, int newToIndex) {
    if (newFromIndex == 0 && newToIndex == size()) {
      return this;
    } else if (newFromIndex < newToIndex) {
      return new RegularImmutableSortedSet<>(
          elements.subList(newFromIndex, newToIndex), comparator);
    } else {

    // The VarHandle, Unsafe, or Java implementation.
    Comparator<byte[]> comparator = UnsignedBytes.lexicographicalComparator();
    Helpers.testComparator(comparator, ordered);
    assertThat(SerializableTester.reserialize(comparator)).isSameInstanceAs(comparator);

    // The Java implementation.
    Comparator<byte[]> javaImpl = UnsignedBytes.lexicographicalComparatorJavaImpl();