assertFalse(underlying.containsKey("a"));

    Set<String> keys = map.keySet();
    keys.remove("b");
    assertFalse(underlying.containsKey("b"));

    Iterator<String> keyIterator = keys.iterator();
    keyIterator.next();
    keyIterator.remove();
    assertFalse(underlying.containsKey("c"));

    Collection<String> values = map.values();
    values.remove("4");
    assertFalse(underlying.containsKey("d"));

    }
  }

  private abstract class Itr<T extends @Nullable Object> implements Iterator<T> {
    final Iterator<Entry<K, Collection<V>>> keyIterator;
    @Nullable K key;
    @Nullable Collection<V> collection;
    Iterator<V> valueIterator;

    Itr() {
      keyIterator = map.entrySet().iterator();
      key = null;
      collection = null;
      valueIterator = Iterators.emptyModifiableIterator();
    }

      LocalCache.this.remove(lastEntry.getKey(), lastEntry.getValue());
      lastEntry = null;
    }
  }

  /** KeyIterator build on top of EntryIterator. */
  final class KeyIterator implements Iterator<K> {
    private EntryIterator iterator;

    KeyIterator() {
      iterator = new EntryIterator();
    }

    @Override
    public boolean hasNext() {
      return iterator.hasNext();

      return cachedKeySet;
    }
    return cachedKeySet = createKeySet();
  }

  ImmutableSet<K> createKeySet() {
    return new ImmutableMapKeySet<K, V>(this);
  }

  UnmodifiableIterator<K> keyIterator() {
    final UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();

   * but ProGuard can't figure out how to eliminate that default when RegularImmutableMap
   * overrides it.
   */
  abstract ImmutableSet<K> createKeySet();

  UnmodifiableIterator<K> keyIterator() {
    UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();

   * but ProGuard can't figure out how to eliminate that default when RegularImmutableMap
   * overrides it.
   */
  abstract ImmutableSet<K> createKeySet();

  UnmodifiableIterator<K> keyIterator() {
    UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();