public Set<Entry<K, V>> entrySet() {
    Set<Entry<K, V>> result = entrySet;
    return (result == null) ? entrySet = new EntrySet() : result;
  }

  class BiMapEntry extends ForwardingMapEntry<K, V> {
    private final Entry<K, V> delegate;

    BiMapEntry(Entry<K, V> delegate) {
      this.delegate = delegate;
    }

    @Override
    protected Entry<K, V> delegate() {
      return delegate;
    }