* to forward to this implementation or a subclass thereof.
   *
   * @since 10.0
   */
  protected class StandardValues extends Maps.Values<K, V> {
    /** Constructor for use by subclasses. */
    public StandardValues() {
      super(ForwardingMap.this);
    }
  }

  /**
   * A sensible definition of {@link #containsValue} in terms of the {@code iterator} method of