code: public static <K, V> ListMultimap<K, V> synchronizedListMultimap(ListMultimap<K, V> multimap) {
      return Synchronized.listMultimap(multimap, null);
    }
docs: Returns a synchronized (thread-safe) {@code ListMultimap} backed by the specified multimap.
  
  <p>You must follow the warnings described in {@link #synchronizedMultimap}.
  
  @param multimap the multimap to be wrapped
  @return a synchronized view of the specified multimap