@Override
public ScheduleDeviationHistogram getScheduleDeviationHistogramForArrivalAndDepartureInstance(
ArrivalAndDepartureInstance instance, int stepSizeInSeconds) {
BlockTripEntry blockTrip = instance.getBlockTrip();
TripEntry trip = blockTrip.getTrip();
AgencyAndId tripId = trip.getId();
ScheduleDeviationHistory history = _scheduleDeviationHistoryDao.getScheduleDeviationHistoryForTripId(tripId);
if( history == null)
return null;