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() {