@SuppressWarnings("unchecked")
  public static <K, V> ImmutableSetMultimap<K, V> of() {
    return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
  }

  /** Returns an immutable multimap containing a single entry. */
  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
    builder.put(k1, v1);
    return builder.build();

  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableSetMultimap<K, V> of() {
    return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
  }

  /** Returns an immutable multimap containing a single entry. */
  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
    builder.put(k1, v1);
    return builder.build();

    assertEquals(ImmutableSetMultimap.of(1, "one"), ImmutableSetMultimap.of("one", 1).inverse());
    assertEquals(
        ImmutableSetMultimap.of(1, "one", 2, "two"),
        ImmutableSetMultimap.of("one", 1, "two", 2).inverse());
    assertEquals(
        ImmutableSetMultimap.of('o', "of", 'f', "of", 't', "to", 'o', "to"),
        ImmutableSetMultimap.of("of", 'o', "of", 'f', "to", 't', "to", 'o').inverse());
  }

                  @Override
                  SetMultimap<String, Integer> filter(SetMultimap<String, Integer> multimap) {
                    ImmutableSetMultimap<String, Integer> badEntries =
                        ImmutableSetMultimap.of("foo", 314, "one", 159, "two", 265, "bar", 358);
                    multimap.putAll(badEntries);
                    return Multimaps.filterEntries(

          .put(ListMultimap.class, ImmutableListMultimap.of())
          .put(ImmutableListMultimap.class, ImmutableListMultimap.of())
          .put(SetMultimap.class, ImmutableSetMultimap.of())
          .put(ImmutableSetMultimap.class, ImmutableSetMultimap.of())
          .put(
              SortedSetMultimap.class,
              Multimaps.unmodifiableSortedSetMultimap(TreeMultimap.create()))

        ImmutableSetMultimap.Builder::combine,
        ImmutableSetMultimap.Builder::build);
  }

  static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableSetMultimap<K, V>> flatteningToImmutableSetMultimap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
    checkNotNull(keyFunction);

          .put(ListMultimap.class, ImmutableListMultimap.of())
          .put(ImmutableListMultimap.class, ImmutableListMultimap.of())
          .put(SetMultimap.class, ImmutableSetMultimap.of())
          .put(ImmutableSetMultimap.class, ImmutableSetMultimap.of())
          .put(
              SortedSetMultimap.class,
              Multimaps.unmodifiableSortedSetMultimap(TreeMultimap.create()))

                  @Override
                  SetMultimap<String, Integer> filter(SetMultimap<String, Integer> multimap) {
                    ImmutableSetMultimap<String, Integer> badEntries =
                        ImmutableSetMultimap.of("foo", 314, "one", 159, "two", 265, "bar", 358);
                    multimap.putAll(badEntries);
                    return Multimaps.filterEntries(

    ImmutableSetMultimap<String, Integer> expected =
        ImmutableSetMultimap.of("one", 1, "won", 1, "two", 2, "too", 2, "three", 3);
    assertEquals(expected, map.asMultimap());
  }

  public void testAsMultimapWhenEmpty() {
    ImmutableMap<String, Integer> map = ImmutableMap.of();
    ImmutableSetMultimap<String, Integer> expected = ImmutableSetMultimap.of();

        }
      } finally {
        monitor.leave();
      }
    }

    ImmutableSetMultimap<State, Service> servicesByState() {
      ImmutableSetMultimap.Builder<State, Service> builder = ImmutableSetMultimap.builder();
      monitor.enter();
      try {
        for (Entry<State, Service> entry : servicesByState.entries()) {