@LazyInit @RetainedWith private transient @Nullable ImmutableBiMap<V, K> lazyInverse;

  @Override
  public ImmutableBiMap<V, K> inverse() {
    if (inverse != null) {
      return inverse;
    } else {
      // racy single-check idiom
      ImmutableBiMap<V, K> result = lazyInverse;
      if (result == null) {
        return lazyInverse = new SingletonImmutableBiMap<>(singleValue, singleKey, this);
      } else {

  public ImmutableBiMap<V, K> inverse() {
    return inverse != null ? inverse : lazyInverse();
  }

  @LazyInit @RetainedWith private transient @Nullable JdkBackedImmutableBiMap<V, K> lazyInverse;

  private ImmutableBiMap<V, K> lazyInverse() {
    JdkBackedImmutableBiMap<V, K> result = lazyInverse;
    return result == null
        ? lazyInverse =
            new JdkBackedImmutableBiMap<>(