* contains(). Verify that these sets are consistent with the elements of their iterator.
   */
  @CanIgnoreReturnValue
  static <T> Set<T> sanityCheckSet(Set<T> set) {
    assertThat(set).hasSize(Iterators.size(set.iterator()));
    for (Object element : set) {
      assertThat(set).contains(element);
    }
    assertThat(set).doesNotContain(new Object());

                          public long skip(long n) {
                            return 0;
                          }
                        };
                      }
                    })
                .iterator());
    assertEquals(0, multi.skip(-1));
    assertEquals(0, multi.skip(-1));
    assertEquals(0, multi.skip(0));
    ByteStreams.skipFully(multi, 20);
    assertEquals(20, multi.read());
  }

    Multiset<Multiset<?>> multiset = HashMultiset.create();
    multiset.add(multiset, 2);
    Multiset<Multiset<?>> copy = SerializableTester.reserialize(multiset);
    assertEquals(2, copy.size());
    assertSame(copy, copy.iterator().next());
  }

  @J2ktIncompatible
  @GwtIncompatible // Only used by @GwtIncompatible code
  private static class MultisetHolder implements Serializable {
    private final Multiset<?> member;

    int copyIntoArray(@Nullable Object[] dst, int offset) {
      return entries.copyIntoArray(dst, offset);
    }

    @Override
    public UnmodifiableIterator<Entry<K, V>> iterator() {
      return entries.iterator();
    }

    @Override
    @GwtIncompatible("Spliterator")
    public Spliterator<Entry<K, V>> spliterator() {
      return entries.spliteratorWithCharacteristics(SPLITERATOR_CHARACTERISTICS);

  }

  protected K getKeyForNullValue() {
    return getEntryNullReplaces().getKey();
  }

  private Entry<K, V> getEntryNullReplaces() {
    Iterator<Entry<K, V>> entries = getSampleElements().iterator();
    for (int i = 0; i < getNullLocation(); i++) {
      entries.next();
    }
    return entries.next();
  }

  /**

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override
  public UnmodifiableIterator<K> iterator() {
    return map.keyIterator();
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return map.containsKey(object);
  }

  @Override
  K get(int index) {

    Multiset<Multiset<?>> multiset = HashMultiset.create();
    multiset.add(multiset, 2);
    Multiset<Multiset<?>> copy = SerializableTester.reserialize(multiset);
    assertEquals(2, copy.size());
    assertSame(copy, copy.iterator().next());
  }

  @J2ktIncompatible
  @GwtIncompatible // Only used by @GwtIncompatible code
  private static class MultisetHolder implements Serializable {
    private final Multiset<?> member;

                          public long skip(long n) {
                            return 0;
                          }
                        };
                      }
                    })
                .iterator());
    assertEquals(0, multi.skip(-1));
    assertEquals(0, multi.skip(-1));
    assertEquals(0, multi.skip(0));
    ByteStreams.skipFully(multi, 20);
    assertEquals(20, multi.read());
  }

    assertFalse(list.contains("chicken"));
    assertEquals(-1, list.indexOf("chicken"));
    assertEquals(-1, list.lastIndexOf("chicken"));
  }

  private static <E> Iterator<E> asIterator(E... elements) {
    return asList(elements).iterator();
  }

  // In GWT, java.util.TreeSet throws ClassCastException when the comparator
  // throws it, unlike the JDK.  Therefore, we accept ClassCastException as a

    void constructorOpenNullCloses() throws Exception {
        // Arrange
        stubAcquireReturnsSelf();
        List<FileEntry[]> pages = List.of(new FileEntry[][] { new FileEntry[] {} });

        // Create iterator where open() returns null by giving null initial
        TestIterator it = TestIterator.create(tree, parent, "*", null, 0, null, pages);

        // Assert