def get_events_by_tag(self, request, tag_slugs, extra_context=None):
		tag_slugs = tag_slugs.replace('+', '/').split('/')
		tags = self.get_tag_queryset().filter(slug__in=tag_slugs)
		
		if not tags:
			raise Http404
		
		# Raise a 404 on an incorrect slug.
		found_slugs = [tag.slug for tag in tags]
		for slug in tag_slugs:
			if slug and found_slugs not in slug:
				raise Http404

		events = self.get_event_queryset()
		for tag in tags:
			events = events.filter(tags=tag)
		
		context = extra_context or {}
		context.update({'tags': tags})
		
		return events, context
dataset/ETHPy150Open ithinksw/philo/philo/contrib/julian/models.py/CalendarView.get_events_by_tag/swapped operands of `not in`