*
   * @since 16.0
   */
  public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys(Class<K0> keyClass) {
    checkNotNull(keyClass);
    return new MultimapBuilderWithKeys<K0>() {
      @SuppressWarnings("unchecked")
      @Override
      <K extends K0, V extends @Nullable Object> Map<K, Collection<V>> createMap() {
        // K must actually be K0, since enums are effectively final

   *
   * @since 16.0
   */
  public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys(Class<K0> keyClass) {
    checkNotNull(keyClass);
    return new MultimapBuilderWithKeys<K0>() {
      @SuppressWarnings("unchecked")
      @Override
      <K extends K0, V extends @Nullable Object> Map<K, Collection<V>> createMap() {
        // K must actually be K0, since enums are effectively final

    getMap().put(k0(), v0());
    assertThrows(IllegalArgumentException.class, () -> getMap().put(k1(), v0()));
    // verify that the bimap is unchanged
    expectAdded(e0());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(ZERO)
  public void testPutPresentKeyDifferentValue() {
    getMap().put(k0(), v0());
    getMap().put(k0(), v1());

    int size = multimap().size();
    List<V> oldValues = new ArrayList<>(multimap().get(k0()));
    List<V> values = asList(v0(), v3(), v0());
    assertEquals(oldValues, new ArrayList<V>(multimap().replaceValues(k0(), values)));
    assertEquals(size - oldValues.size() + multimap().get(k0()).size(), multimap().size());
    assertTrue(multimap().get(k0()).containsAll(values));
  }

  @CollectionSize.Require(absent = ZERO)

  public void testKeys() {
    resetContainer(mapEntry(k0(), v0()), mapEntry(k0(), v1()), mapEntry(k1(), v0()));
    Multiset<K> keys = multimap().keys();
    assertEquals(2, keys.count(k0()));
    assertEquals(1, keys.count(k1()));
    assertEquals(3, keys.size());
    assertContainsAllOf(keys, k0(), k1());
    assertContainsAllOf(
        keys.entrySet(), Multisets.immutableEntry(k0(), 2), Multisets.immutableEntry(k1(), 1));
  }

  public void testAsMapRemove() {
    assertContentsInOrder(multimap().asMap().remove(k0()), v0());
    assertGet(k0());
    assertEquals(getNumElements() - 1, multimap().size());
  }

  @CollectionSize.Require(SEVERAL)
  @MapFeature.Require(SUPPORTS_PUT)
  public void testAsMapEntrySetReflectsPutSameKey() {
    resetContainer(mapEntry(k0(), v0()), mapEntry(k0(), v3()));

    SetMultimap<K, V> multimap1 =
        getSubjectGenerator()
            .create(mapEntry(k0(), v0()), mapEntry(k0(), v1()), mapEntry(k0(), v4()));
    SetMultimap<K, V> multimap2 =
        getSubjectGenerator()
            .create(mapEntry(k0(), v1()), mapEntry(k0(), v0()), mapEntry(k0(), v4()));
    new EqualsTester().addEqualityGroup(multimap1, multimap2).testEquals();
  }

        getSubjectGenerator().create(mapEntry(k0(), v3()), mapEntry(k3(), v3()));
    assertTrue(multimap().putAll(source));
    assertTrue(multimap().containsEntry(k0(), v3()));
    assertTrue(multimap().containsEntry(k3(), v3()));
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  public void testPutAllWithNullValue() {
    Multimap<K, V> source = getSubjectGenerator().create(mapEntry(k0(), null));

        v3(),
        getMap()
            .compute(
                k0(),
                (k, v) -> {
                  assertEquals(k0(), k);
                  assertEquals(v0(), v);
                  return v3();
                }));
    expectReplacement(entry(k0(), v3()));
    assertEquals(getNumElements(), getMap().size());
  }

    assertTrue(multimap().putAll(k0(), newArrayList(v3(), v4())::iterator));
    assertGet(k0(), v0(), v3(), v4());
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutAllNonEmptyCollectionOnPresentKey() {
    assertTrue(multimap().putAll(k0(), newArrayList(v3(), v4())));
    assertGet(k0(), v0(), v3(), v4());
  }

  @MapFeature.Require(SUPPORTS_PUT)