*/
  public static <K, V> ImmutableMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) {
    if (multimap instanceof ImmutableMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableMultimap<K, V> kvMultimap = (ImmutableMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }

   */
  public static <K, V> ImmutableMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) {
    if (multimap instanceof ImmutableMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableMultimap<K, V> kvMultimap = (ImmutableMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }

  }

  public void testEquals() {
    new EqualsTester()
        .addEqualityGroup(ImmutableMultimap.of(), ImmutableMultimap.of())
        .addEqualityGroup(ImmutableMultimap.of(1, "a"), ImmutableMultimap.of(1, "a"))
        .addEqualityGroup(
            ImmutableMultimap.of(1, "a", 2, "b"), ImmutableMultimap.of(2, "b", 1, "a"))
        .testEquals();
  }

  @J2ktIncompatible
  @GwtIncompatible // reflection

  }

  public void testInvertFrom() {
    ImmutableMultimap<Integer, String> empty = ImmutableMultimap.of();

    // typical usage example - sad that ArrayListMultimap.create() won't work
    Multimap<String, Integer> multimap =
        Multimaps.invertFrom(empty, ArrayListMultimap.<String, Integer>create());
    assertTrue(multimap.isEmpty());

    ImmutableMultimap<Integer, String> single =

    assertFreshInstance(new TypeToken<ImmutableSortedMap<String, Integer>>() {});
  }

  public void testImmutableMultimap() {
    assertFreshInstance(new TypeToken<ImmutableMultimap<String, Integer>>() {});
    assertNotInstantiable(new TypeToken<ImmutableMultimap<EmptyEnum, String>>() {});
  }

  public void testImmutableListMultimap() {
    assertFreshInstance(new TypeToken<ImmutableListMultimap<String, Integer>>() {});
  }

   *
   * <p>Because an inverse of a list multimap can contain multiple pairs with the same key and
   * value, this method returns an {@code ImmutableListMultimap} rather than the {@code
   * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
   *
   * @since 11.0
   */
  @Override
  public ImmutableListMultimap<V, K> inverse() {
    ImmutableListMultimap<V, K> result = inverse;

      derivedFeatures.remove(CollectionFeature.SERIALIZABLE);
    }
    return derivedFeatures;
  }

  private static final ImmutableMultimap<Feature<?>, Feature<?>> GET_FEATURE_MAP =
      ImmutableMultimap.<Feature<?>, Feature<?>>builder()
          .put(
              MapFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION,
              CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION)

      derivedFeatures.remove(CollectionFeature.SERIALIZABLE);
    }
    return derivedFeatures;
  }

  private static final ImmutableMultimap<Feature<?>, Feature<?>> GET_FEATURE_MAP =
      ImmutableMultimap.<Feature<?>, Feature<?>>builder()
          .put(
              MapFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION,
              CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION)

   *
   * <p>Because an inverse of a list multimap can contain multiple pairs with the same key and
   * value, this method returns an {@code ImmutableListMultimap} rather than the {@code
   * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
   *
   * @since 11.0
   */
  @Override
  public ImmutableListMultimap<V, K> inverse() {
    ImmutableListMultimap<V, K> result = inverse;

   *
   * <p>Because an inverse of a set multimap cannot contain multiple pairs with the same key and
   * value, this method returns an {@code ImmutableSetMultimap} rather than the {@code
   * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
   */
  @Override
  public ImmutableSetMultimap<V, K> inverse() {
    ImmutableSetMultimap<V, K> result = inverse;
    return (result == null) ? (inverse = invert()) : result;
  }