How to use the eventy.models.EventTime.upcoming_objects.filter function in eventy

def get_queryset(self):
        try:
            if self.kwargs['cal_slug']:
                return EventTime.upcoming_objects.filter(event__calendar__slug=self.kwargs['cal_slug'])
        except:
            pass

        try:
            if self.kwargs['slug']:
                return EventTime.upcoming_objects.filter(event__slug=self.kwargs['slug'])
        except:
            return EventTime.upcoming_objects.all()