@RetainedWith
  transient AbstractBiMap<V, K> inverse;

  /** Package-private constructor for creating a map-backed bimap. */
  AbstractBiMap(Map<K, V> forward, Map<V, K> backward) {
    setDelegates(forward, backward);
  }

  /** Private constructor for inverse bimap. */
  private AbstractBiMap(Map<K, V> backward, AbstractBiMap<V, K> forward) {
    delegate = backward;
    inverse = forward;
  }

 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible(emulated = true)
@J2ktIncompatible
@ElementTypesAreNonnullByDefault
public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>> extends AbstractBiMap<K, V> {
  /*
   * J2CL's EnumMap does not need the Class instance, so we can use Object.class instead. (Or we
   * could use null, but that messes with our nullness checking, including under J2KT. We could

 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible(emulated = true)
@J2ktIncompatible
@ElementTypesAreNonnullByDefault
public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>> extends AbstractBiMap<K, V> {
  /*
   * J2CL's EnumMap does not need the Class instance, so we can use Object.class instead. (Or we
   * could use null, but that messes with our nullness checking, including under J2KT. We could

   * as implementation details.
   *
   * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
   * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
   */
  @J2ktIncompatible // serialization
  private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {
    SerializedForm(ImmutableBiMap<K, V> bimap) {
      super(bimap);
    }

   * as implementation details.
   *
   * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
   * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
   */
  @J2ktIncompatible // serialization
  private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {
    SerializedForm(ImmutableBiMap<K, V> bimap) {
      super(bimap);
    }