Invalidate Django cached_property in signal handler without introducing unnecessary queries

Let's say I have the following Django models:

class Team(models.Model):
    users = models.ManyToManyField(User, through="TeamUser")

    @cached_property
    def total_points(self):
        return self.teamuser_set.aggregate(models.Sum("points"))["points__sum"] or 0

class TeamUser(models.Model):
    team = models.ForeignKey(Team, on_delete=models.CASCADE)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    points = models.IntegerField()

I want to create a signal handler that will invalidate the team.total_points cache when TeamUser object is created/updated/deleted.

I started with the following signal handler. Note the Django docs recommended the del instance.prop call.

@receiver(post_save, sender=models.TeamUser)
@receiver(post_delete, sender=models.TeamUser)
def invalidate_cache(**kwargs):
    try:
        del kwargs["instance"].team.total_points
    except AttributeError:
        pass

And some tests. Note I'm using pytest-django.

def test_create_team_users(django_assert_num_queries):
    user = factories.UserFactory()
    team = factories.TeamFactory()
    assert team.total_points == 0

    with django_assert_num_queries(1):
        TeamUser.objects.create(team=team, user=user, points=2)
    assert team.total_points == 2

    with django_assert_num_queries(1):
        TeamUser.objects.create(team=team, user=user, points=3)
    assert team.total_points == 5

def test_delete_all_team_users(django_assert_num_queries):
    user = factories.UserFactory()
    team = factories.TeamFactory()
    for _ in range(10):
        TeamUser.objects.create(team=team, user=user, points=2)

    with django_assert_num_queries(2):
        TeamUser.objects.all().delete()
    assert team.total_points == 0

The test_create_team_users test passed but the test_delete_all_team_users test failed because the query count is 12 instead of 2. Yikes! Looks like an N+1 query.

To prevent this, I updated my signal handler to only invalidate the team.total_points cache if the user object is cached on the TeamUser object. I found the is_cached method in this SO answer.

@receiver(post_save, sender=models.TeamUser)
@receiver(post_delete, sender=models.TeamUser)
def invalidate_cache(sender, instance, **kwargs):
    if sender.team.is_cached(instance):
        try:
            del instance.team.total_points
        except AttributeError:
            pass

Now both tests pass!

Does this correctly invalidate the team.total_points cache in all cases? Is there an edge case I'm missing?

from Invalidate Django cached_property in signal handler without introducing unnecessary queries