return new Maps.NavigableKeySet<>(this);
  }

  @Override
  public Set<K> keySet() {
    return navigableKeySet();
  }

  @Override
  public NavigableSet<K> descendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return new DescendingMap();
  }

    return new Maps.NavigableKeySet<>(this);
  }

  @Override
  public Set<K> keySet() {
    return navigableKeySet();
  }

  @Override
  public NavigableSet<K> descendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return new DescendingMap();
  }