code: public void putAll(K key, Collection<? extends V> values) {
  		if (values.isEmpty()) {
  			return;
  		}
  
  		key = sanitizeKey(key);
  		List<V> list = map.get(key);
  		if (list == null) {
  			list = new ArrayList<V>();
  			map.put(key, list);
  		}
  		list.addAll(values);
  	}
docs: Adds multiple values to the multimap.
  @param key the key
  @param values the values to add