@Override
 protected void addNodes(final PrintWriter writer, final List<Integer> tripIds) {
   writer.print("\"nodes\": [");
   final List<TripInstance> tripInstances =
       tripInstanceDao.getTripInstancesForTripIds(tripIds, 20);
   doAddNodes(writer, tripInstances);
 }
 @Override
 protected void addNodes(final PrintWriter writer, final int tripId, final long serviceDate) {
   writer.print("\"nodes\": [");
   final TripInstance tripInstance = tripInstanceDao.getTripInstance(tripId, serviceDate);
   final List<TripInstance> tripInstances = new ArrayList<>();
   tripInstances.add(tripInstance);
   doAddNodes(writer, tripInstances);
 }
 @Override
 protected void addNodes(final PrintWriter writer) {
   writer.print("\"nodes\": [");
   final List<TripInstance> tripInstances = tripInstanceDao.getTripInstances();
   doAddNodes(writer, tripInstances);
 }