} catch (RuntimeException tolerated) {
      // GWT's TreeMap.keySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRetainAllNullFromEmpty() {
    try {
      super.testKeySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.keySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override

    }
  }

  public void testAsMapGetImplementsSet() {
    for (K key : multimap().keySet()) {
      assertTrue(multimap().asMap().get(key) instanceof Set);
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testAsMapRemoveImplementsSet() {
    List<K> keys = new ArrayList<>(multimap().keySet());
    for (K key : keys) {
      resetCollection();

    checkArgument(!delegate.isEmpty());
  }

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

  @Override
  Spliterator<K> keySpliterator() {
    return delegate.keySet().spliterator();
  }

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

  @Override

    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);

    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)

  }


  public void testKeySet_populated() {
    for (LoadingCache<Object, Object> cache : caches()) {
      Set<Object> keys = cache.asMap().keySet();
      List<Entry<Object, Object>> warmed = warmUp(cache);

      Set<Object> expected = Maps.newHashMap(cache.asMap()).keySet();
      assertThat(keys).containsExactlyElementsIn(expected);
      assertThat(keys.toArray()).asList().containsExactlyElementsIn(expected);

   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in sorted order.
   *
   * <p>For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be
   * safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be

    }
  }

  public void testAsMapGetImplementsSet() {
    for (K key : multimap().keySet()) {
      assertTrue(multimap().asMap().get(key) instanceof Set);
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testAsMapRemoveImplementsSet() {
    List<K> keys = new ArrayList<>(multimap().keySet());
    for (K key : keys) {
      resetCollection();

    this(new TreeMap<K, V>(map));
  }

  private SafeTreeMap(NavigableMap<K, V> delegate) {
    this.delegate = delegate;
    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override

    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #keySet()
    assertSetIsUnmodifiable(multimap.keySet(), sampleKey);
    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #get()
    if (!multimap.isEmpty()) {
      K key = multimap.keySet().iterator().next();
      assertCollectionIsUnmodifiable(multimap.get(key), sampleValue);