docs: @Override
    public void initState(State state) {
      this.state = state;
      // initalize internal windowing state
      super.initState(this.state);
      // initialize user defined state
      if (!this.state.containsKey(USER_STATE)) {
        this.state.put(USER_STATE, new HashMapState<K, V>());
      }
      this.statefulWindowedBolt.initState((State<K, V>) this.state.get(USER_STATE));
    }