code: public boolean put(K key, V value) {
  	Set<V> values = map.get(key);
  	if (values == null) {
  	    values = new HashSet<V>();
  	    map.put(key, values);
  	}
  	boolean added = values.add(value);
  	if (added) {
  	    range++;
  	    if (parent != null) {
  		parent.updateParentRange(1);
  	    }
  	}
  	return added;
      }
docs: {@inheritDoc}