public Set<K> values() {
      return forward.keySet();
    }

    private transient Set<Entry<V, K>> inverseEntrySet;

    @Override
    public Set<Entry<V, K>> entrySet() {
      Set<Entry<V, K>> result = inverseEntrySet;
      return (result == null) ? inverseEntrySet = new InverseEntrySet<K, V>(forward) : result;
    }

    @GwtIncompatible("serialization")

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

    @Override
    ImmutableSet<Entry<V, K>> createEntrySet() {
      return new InverseEntrySet();
    }

    final class InverseEntrySet extends ImmutableMapEntrySet<V, K> {
      @Override
      ImmutableMap<V, K> map() {
        return Inverse.this;
      }

      @Override
      boolean isHashCodeFast() {