return (SortedMap<R, Map<C, V>>) backingMap;
  }

  /**
   * {@inheritDoc}
   *
   * <p>This method returns a {@link SortedSet}, instead of the {@code Set} specified in the {@link
   * Table} interface.
   */
  @Override
  public SortedSet<R> rowKeySet() {
    return (SortedSet<R>) rowMap().keySet();
  }

  /**
   * {@inheritDoc}
   *

    super(map);
  }

  @Override
  abstract SortedSet<V> createCollection();

  @Override
  SortedSet<V> createUnmodifiableEmptyCollection() {
    return unmodifiableCollectionSubclass(createCollection());
  }

  @Override
  <E extends @Nullable Object> SortedSet<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    if (collection instanceof NavigableSet) {

    ms.add("a", 1);
    ms.add("b", 3);
    ms.add("c", 2);
    ms.add("d", 1);
    ms.add("e", 3);
    ms.add("f", 2);

    SortedSet<String> elementSet = ms.elementSet();
    assertThat(elementSet).containsExactly("a", "b", "c", "d", "e", "f").inOrder();
    SortedSet<String> subset = elementSet.subSet("b", "f");
    assertThat(subset).containsExactly("b", "c", "d", "e").inOrder();

    assertTrue(subset.remove("c"));

    SortedSet<String> set = of("e", "a", "f", "b", "d", "c");
    SortedSet<String> subset = set.subSet("c", "e");
    SortedSet<String> copy = copyOf(subset);
    assertEquals(subset, copy);
  }

  public void testCopyOf_headSet() {
    SortedSet<String> set = of("e", "a", "f", "b", "d", "c");
    SortedSet<String> headset = set.headSet("d");
    SortedSet<String> copy = copyOf(headset);

  }

  private static boolean hasSameComparator(Iterable<?> elements, Comparator<?> comparator) {
    if (elements instanceof SortedSet) {
      SortedSet<?> sortedSet = (SortedSet<?>) elements;
      Comparator<?> comparator2 = sortedSet.comparator();
      return (comparator2 == null)
          ? comparator == Ordering.natural()
          : comparator.equals(comparator2);
    }
    return false;
  }

    @Override
    protected SortedSet<Integer> create(Integer[] elements) {
      return checkedCreate(nullCheckedTreeSet(elements));
    }
  }

  public static class ContiguousSetHeadsetGenerator extends AbstractContiguousSetGenerator {
    @Override
    protected SortedSet<Integer> create(Integer[] elements) {
      SortedSet<Integer> set = nullCheckedTreeSet(elements);

        .testForwarding(
            SortedSet.class,
            new Function<SortedSet, SortedSet>() {
              @Override
              public SortedSet apply(SortedSet delegate) {
                return wrap(delegate);
              }
            });
  }

  public void testEquals() {
    SortedSet<String> set1 = ImmutableSortedSet.of("one");
    SortedSet<String> set2 = ImmutableSortedSet.of("two");

 */
@SuppressWarnings("JdkObsolete")
public abstract class ForwardingSortedSet<E extends @Nullable Object> extends ForwardingSet<E>
    implements SortedSet<E> {

  /** Constructor for use by subclasses. */
  protected ForwardingSortedSet() {}

  @Override
  protected abstract SortedSet<E> delegate();

  @Override
  public @Nullable Comparator<? super E> comparator() {
    return delegate().comparator();
  }

  @Override

    super(map);
  }

  @Override
  abstract SortedSet<V> createCollection();

  @Override
  SortedSet<V> createUnmodifiableEmptyCollection() {
    return unmodifiableCollectionSubclass(createCollection());
  }

  @Override
  <E extends @Nullable Object> SortedSet<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    if (collection instanceof NavigableSet) {

  public Test testsForTreeSetWithComparator() {
    return NavigableSetTestSuiteBuilder.using(
            new TestStringSortedSetGenerator() {
              @Override
              public SortedSet<String> create(String[] elements) {
                SortedSet<String> set = new TreeSet<>(arbitraryNullFriendlyComparator());
                Collections.addAll(set, elements);
                return set;
              }
            })