* descendingMap}, you may wish to override {@code descendingKeySet} to forward to this
   * implementation.
   */
  protected NavigableSet<K> standardDescendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  /**
   * A sensible definition of {@link #subMap(Object, Object)} in terms of {@link #subMap(Object,

   * descendingMap}, you may wish to override {@code descendingKeySet} to forward to this
   * implementation.
   */
  protected NavigableSet<K> standardDescendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  /**
   * A sensible definition of {@link #subMap(Object, Object)} in terms of {@link #subMap(Object,