checkNotNull(multimapSupplier);
    return Collector.of(
        multimapSupplier,
        (multimap, input) -> multimap.put(keyFunction.apply(input), valueFunction.apply(input)),
        (multimap1, multimap2) -> {
          multimap1.putAll(multimap2);
          return multimap1;
        });
  }

  static <
          T extends @Nullable Object,
          K extends @Nullable Object,

    assertEquals(0, multimap().size());
    assertEmpty(multimap());
    assertEquals(multimap(), getSubjectGenerator().create());
    assertEmpty(multimap().entries());
    assertEmpty(multimap().asMap());
    assertEmpty(multimap().keySet());
    assertEmpty(multimap().keys());
    assertEmpty(multimap().values());
    for (K key : sampleKeys()) {
      assertGet(key);
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)

  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutTwoElements() {
    int size = getNumElements();

    List<V> values = copyToList(multimap().get(k0()));

    assertTrue(multimap().put(k0(), v1()));
    assertTrue(multimap().put(k0(), v2()));

    values.add(v1());
    values.add(v2());

    assertGet(k0(), values);
    assertEquals(size + 2, multimap().size());
  }

    Collection<V> result = multimap().get(k0());
    assertTrue(result.add(v3()));
    assertTrue(multimap().containsKey(k0()));
    assertEquals(getNumElements() + 1, multimap().size());
    assertTrue(multimap().containsEntry(k0(), v3()));
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPropagatesAddAllToMultimap() {
    Collection<V> result = multimap().get(k0());

    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);
    multimap.put("foo", 3);
    assertEquals(ImmutableSet.of(1, 3), multimap.get("foo"));
    assertEquals(2, multimap.expectedValuesPerKey);
  }

  public void testCreateFromMultimap() {
    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);

    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);
    multimap.put("foo", 3);
    assertEquals(ImmutableSet.of(1, 3), multimap.get("foo"));
    assertEquals(2, multimap.expectedValuesPerKey);
  }

  public void testCreateFromMultimap() {
    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);

    assertContentsAnyOrder(multimap().get(k0()), v1(), v2());
    assertTrue(multimap().containsKey(k0()));
    assertFalse(multimap().containsEntry(k0(), v0()));
    assertTrue(multimap().containsEntry(k0(), v2()));
    assertEquals(oldSize + 1, multimap().size());
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testReflectsMultimapRemove() {

   */
  @SuppressWarnings("UndefinedEquals")
  public void testRetainAllPropagatesToMultimap() {
    multimap().entries().retainAll(singleton(mapEntry(k0(), v0())));
    assertEquals(getSubjectGenerator().create(mapEntry(k0(), v0())), multimap());
    assertEquals(1, multimap().size());
    assertTrue(multimap().containsEntry(k0(), v0()));
  }

  @CollectionSize.Require(ONE)

 * already in the multimap has no effect. This interface does not specify the ordering of the
 * multimap's keys. See the {@link Multimap} documentation for information common to all multimaps.
 *
 * <p>The {@link #get}, {@link #removeAll}, and {@link #replaceValues} methods each return a {@link
 * SortedSet} of values, while {@link Multimap#entries()} returns a {@link Set} of map entries.

   * Multimap} interface.
   */
  @CanIgnoreReturnValue
  @Override
  public List<V> replaceValues(@ParametricNullness K key, Iterable<? extends V> values) {
    return (List<V>) super.replaceValues(key, values);
  }

  /**
   * Stores a key-value pair in the multimap.
   *
   * @param key key to store in the multimap
   * @param value value to store in the multimap