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"));

                    final Iterator<Entry<String, String>> keyIterator =
                            storage.entrySet().iterator();

                    public boolean hasNext() {
                        return keyIterator.hasNext();
                    }

                    public Entry<String, String> next() {
                        final Entry<String, String> entry = keyIterator.next();

      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();

    @Override
    public boolean retainAll(Collection<?> keysToRetain) {
      return standardRetainAll(keysToRetain);
    }

    @Override
    public Iterator<K> iterator() {
      return Maps.keyIterator(entrySet().iterator());
    }
  }

  @LazyInit @CheckForNull private transient Set<V> valueSet;

  @Override
  public Set<V> values() {
    /*

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

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