def appliesToEvent(self, event):
        ''' Check whether this guest list is applicable to an event. '''
        return (
            event in self.individualEvents.all() or
            event.session in self.eventSessions.all() or
            event.category in self.seriesCategories.all() or
            event.category in self.eventCategories.all()
        )
Check whether this guest list is applicable to an event.