@Override
    public int hashCode() {
      return Sets.hashCodeImpl(this);
    }

    @Override
    public boolean equals(@CheckForNull Object obj) {
      return Sets.equalsImpl(this, obj);
    }
  }

  abstract Iterator<Entry<K, V>> entryIterator();

  @LazyInit @CheckForNull private transient Set<K> keySet;

  @Override
  public Set<K> keySet() {

    @Override
    public int hashCode() {
      return Sets.hashCodeImpl(this);
    }

    @Override
    public boolean equals(@CheckForNull Object obj) {
      return Sets.equalsImpl(this, obj);
    }
  }

  abstract Iterator<Entry<K, V>> entryIterator();

  Spliterator<Entry<K, V>> entrySpliterator() {
    return Spliterators.spliterator(