code: public List<StopTime> getStopTimesForStop (String stop_id) {
          SortedSet<Tuple2<String, Tuple2>> index = this.stopStopTimeSet
                  .subSet(new Tuple2<>(stop_id, null), new Tuple2(stop_id, Fun.HI));
  
          return index.stream()
                  .map(tuple -> this.stop_times.get(tuple.b))
                  .collect(Collectors.toList());
      }
docs: Get list of stop_times for a given stop_id.