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