* {@link SortedMultiset#entrySet}, and {@link SortedMultiset#remove(Object, int)}. In many
   * situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this
   * implementation or a subclass thereof.
   */
  protected class StandardElementSet extends SortedMultisets.ElementSet<E> {
    /** Constructor for use by subclasses. */
    public StandardElementSet() {
      super(ForwardingSortedMultiset.this);