assertContainsAllOf(
        keys.entrySet(), Multisets.immutableEntry((K) null, 2), Multisets.immutableEntry(k1(), 1));
  }

  public void testKeysElementSet() {
    assertEquals(multimap().keySet(), multimap().keys().elementSet());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeysRemove() {
    int original = multimap().keys().remove(k0(), 1);

  @CollectionSize.Require(SEVERAL)
  public void testClearConcurrentWithKeySetIteration() {
    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<K> iterator = getMap().keySet().iterator();
          getMap().clear();
          iterator.next();
        });
  }

  @MapFeature.Require({FAILS_FAST_ON_CONCURRENT_MODIFICATION, SUPPORTS_REMOVE})
  @CollectionSize.Require(SEVERAL)

    Multimap<String, Integer> filtered = filterValues(keyFiltered, VALUE_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));
    assertTrue(filtered.keySet().retainAll(asList("cat", "dog")));
    assertEquals(0, filtered.size());
  }

  // TODO(jlevy): Many more tests needed.

      return size == keyToIndex().size();
    }

    K getKey(int index) {
      return keyToIndex().keySet().asList().get(index);
    }

    @CheckForNull
    abstract V getValue(int keyIndex);

    @Override
    ImmutableSet<K> createKeySet() {
      return isFull() ? keyToIndex().keySet() : super.createKeySet();
    }

    @Override
    public int size() {
      return size;
    }

                value = e.getValue().toString();
            }
            itemList.add(createItem(k, value));
        });
        if (fessConfig instanceof final ObjectiveConfig config) {
            config.keySet().stream().forEach(k -> {
                final String value;
                if (isMaskedValue(k)) {
                    value = MASKED_VALUE;
                } else {
                    value = config.get(k);

    Multimap<String, Integer> filtered = filterValues(keyFiltered, VALUE_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));
    assertTrue(filtered.keySet().retainAll(asList("cat", "dog")));
    assertEquals(0, filtered.size());
  }

  // TODO(jlevy): Many more tests needed.

    Map<String, Integer> map = ImmutableSortedMap.of("one", 1, "two", 2, "three", 3);
    SerializableTester.reserializeAndAssert(map.entrySet());
    SerializableTester.reserializeAndAssert(map.keySet());
    assertEquals(
        Lists.newArrayList(map.values()),
        Lists.newArrayList(SerializableTester.reserialize(map.values())));
  }

    Map<String, Integer> map = ImmutableSortedMap.of("one", 1, "two", 2, "three", 3);
    SerializableTester.reserializeAndAssert(map.entrySet());
    SerializableTester.reserializeAndAssert(map.keySet());
    assertEquals(
        Lists.newArrayList(map.values()),
        Lists.newArrayList(SerializableTester.reserialize(map.values())));
  }

    this.delegate = delegate;
    checkArgument(!delegate.isEmpty());
  }

  @Override
  UnmodifiableIterator<K> keyIterator() {
    return Iterators.unmodifiableIterator(delegate.keySet().iterator());
  }

  @Override
  public int size() {
    return delegate.size();
  }

  @Override
  public boolean containsKey(@CheckForNull Object key) {
    return delegate.containsKey(key);
  }

    assertEquals(3, multimap().size());
    assertEquals(3, multimap().entries().size());
    assertEquals(3, multimap().keys().size());

    assertEquals(1, multimap().keySet().size());
    assertEquals(1, multimap().asMap().size());
  }