assertEquals(tree, copyFromTree);
    assertSame(Ordering.natural(), copyFromTree.keyComparator());
    assertSame(Ordering.natural(), copyFromTree.valueComparator());
    assertSame(Ordering.natural(), copyFromTree.get(1.0).comparator());
  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {

  }

  @Test
  public void nodeOrder_natural() {
    MutableGraph<Integer> graph =
        GraphBuilder.directed().nodeOrder(ElementOrder.<Integer>natural()).build();

    addNodes(graph);

    assertThat(graph.nodeOrder()).isEqualTo(ElementOrder.sorted(Ordering.<Integer>natural()));
    assertThat(graph.nodes()).containsExactly(1, 3, 4).inOrder();
  }

  @Test

    assertTrue(Comparators.isInOrder(Collections.singleton(1), Ordering.natural()));
    assertTrue(Comparators.isInOrder(Collections.<Integer>emptyList(), Ordering.natural()));
  }

  public void testIsInStrictOrder() {
    assertFalse(Comparators.isInStrictOrder(asList(5, 3, 0, 9), Ordering.natural()));
    assertFalse(Comparators.isInStrictOrder(asList(0, 5, 3, 9), Ordering.natural()));

   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  private static final ImmutableSortedMap<Comparable<?>, Object> NATURAL_EMPTY_MAP =
      new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.<Object>of());

  static <K, V> ImmutableSortedMap<K, V> emptyMap(Comparator<? super K> comparator) {
    if (Ordering.natural().equals(comparator)) {
      return of();

    assertTrue(Comparators.isInOrder(Collections.singleton(1), Ordering.natural()));
    assertTrue(Comparators.isInOrder(Collections.<Integer>emptyList(), Ordering.natural()));
  }

  public void testIsInStrictOrder() {
    assertFalse(Comparators.isInStrictOrder(asList(5, 3, 0, 9), Ordering.natural()));
    assertFalse(Comparators.isInStrictOrder(asList(0, 5, 3, 9), Ordering.natural()));

  /**
   * Creates an empty {@code TreeMultimap} ordered by the natural ordering of its keys and values.
   */
  @SuppressWarnings("rawtypes") // https://github.com/google/guava/issues/989
  public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create() {
    return new TreeMultimap<>(Ordering.natural(), Ordering.natural());
  }

  /**

    // Before JDK6 (including under GWT), the TreeMap keySet is a plain Set.
    if (Maps.newTreeMap().keySet() instanceof SortedSet) {
      assertTrue(SortedIterables.hasSameComparator(Ordering.natural(), Maps.newTreeMap().keySet()));
    }
    assertTrue(
        SortedIterables.hasSameComparator(

    assertEquals(tree, copyFromTree);
    assertSame(Ordering.natural(), copyFromTree.keyComparator());
    assertSame(Ordering.natural(), copyFromTree.valueComparator());
    assertSame(Ordering.natural(), copyFromTree.get(1.0).comparator());
  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {

  }

  @Test
  public void nodeOrder_natural() {
    MutableGraph<Integer> graph =
        GraphBuilder.directed().nodeOrder(ElementOrder.<Integer>natural()).build();

    addNodes(graph);

    assertThat(graph.nodeOrder()).isEqualTo(ElementOrder.sorted(Ordering.<Integer>natural()));
    assertThat(graph.nodes()).containsExactly(1, 3, 4).inOrder();
  }

  @Test

    throw new UnsupportedOperationException();
  }

  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  @SuppressWarnings("unchecked")
  private static final ImmutableSortedSet<Object> NATURAL_EMPTY_SET =
      new RegularImmutableSortedSet<Object>(
          new TreeSet<Object>((Comparator<Object>) NATURAL_ORDER), false);

  static <E> ImmutableSortedSet<E> emptySet(Comparator<? super E> comparator) {