}

  @Override
  @J2ktIncompatible
  @GwtIncompatible
    Object writeReplace() {
    return new KeySetSerializedForm<K>(map);
  }

  @GwtIncompatible
  @J2ktIncompatible
  private static final class KeySetSerializedForm<K> implements Serializable {
    final ImmutableMap<K, ?> map;

    KeySetSerializedForm(ImmutableMap<K, ?> map) {
      this.map = map;
    }

    Object readResolve() {