code: public boolean putMany(K key, Collection<V> values) {
          // Short circuit when adding empty values to avoid adding a key with an
          // empty mapping
          if (values.isEmpty())
              return false;
  	Set<V> vals = map.get(key);
  	if (vals == null) {
  	    vals = new HashSet<V>();
  	    map.put(key, vals);
  	}
  	int oldSize = vals.size();
  	boolean added = vals.addAll(values);
  	range += (vals.size() - oldSize);
  	return added;
      }
docs: {@inheritDoc}