* #synchronizedMultimap}.
   *
   * <p>Call this method only when the simpler methods {@link ArrayListMultimap#create()}, {@link
   * HashMultimap#create()}, {@link LinkedHashMultimap#create()}, {@link
   * LinkedListMultimap#create()}, {@link TreeMultimap#create()}, and {@link
   * TreeMultimap#create(Comparator, Comparator)} won't suffice.
   *