### Question:
GuavaCollectors { public static <K, V> BiCollector<K, V, ImmutableSetMultimap<K, V>> toImmutableSetMultimap() { return ImmutableSetMultimap::toImmutableSetMultimap; } private  GuavaCollectors(); static BiCollector<K, V, ImmutableMap<K, V>> toImmutableMap(); static BiCollector<K, V, ImmutableMap<K, V>> toImmutableMap(
      BinaryOperator<V> valueMerger); static Collector<V, ?, ImmutableMap<K, V>> indexingBy(
      Function<? super V, ? extends K> indexingFunction); static BiCollector<K, V1, ImmutableMap<K, V>> toImmutableMap(
      Collector<V1, ?, V> valueCollector); static BiCollector<K, V, ImmutableSortedMap<K, V>> toImmutableSortedMap(
      Comparator<? super K> comparator, BinaryOperator<V> valueMerger); static BiCollector<K, V, ImmutableSortedMap<K, V>> toImmutableSortedMap(
      Comparator<? super K> comparator); static BiCollector<K, V, M> toMultimap(
      Supplier<M> multimapSupplier); static BiCollector<K, V, ImmutableListMultimap<K, V>> toImmutableListMultimap(); static BiCollector<K, T, ImmutableListMultimap<K, V>> flatteningToImmutableListMultimap(
          Function<? super T, ? extends Stream<? extends V>> flattener); static BiCollector<K, V, ImmutableSetMultimap<K, V>> toImmutableSetMultimap(); static BiCollector<K, T, ImmutableSetMultimap<K, V>> flatteningToImmutableSetMultimap(
          Function<? super T, ? extends Stream<? extends V>> flattener); static BiCollector<K, V, ImmutableMultiset<K>> toImmutableMultiset(
      ToIntFunction<? super V> countFunction); static BiCollector<K, V, ImmutableBiMap<K, V>> toImmutableBimap(); static BiCollector<R, BiStream<? extends C, ? extends V>, ImmutableTable<R, C, V>> toImmutableTable();  }### Answer:
@Test public void testToImmutableSetMultimap_covariance() { ImmutableSetMultimap<Object, String> map = BiStream.of(1, "one", 1, "uno").collect(toImmutableSetMultimap()); assertThat(map).containsExactly(1, "one", 1, "uno"); }
@Test public void testToSetMultimap() { assertThat(BiStream.of("one", 1, "two", 2).collect(toImmutableSetMultimap())) .containsExactly("one", 1, "two", 2); }