How to display a filtered admin list based off of a count of foreign keys in django
===

I am trying to define a proxy model for my admin view and have it only show objects that have a certain amount of foreign key values.

This is what I'm trying, but I'm not able to filter on yVotes:

    class Post(models.Model):
        title = models.CharField(max_length=512)

    class PostVote(models.Model):
        post = models.ForeignKey(Post)
        vote = models.CharField(max_length=1)

    class VotedPost(models.Post):
        def _yVotes(self):
            return models.PostVote.objects.filter(post=self, vote='Y').count()
        yVotes = property(_yVotes)
        class Meta:
            proxy = True 

    class VotedPostAdmin(PostAdmin):
        list_display = ('title', 'yVotes')
        def queryset(self, request):
            return self.model.objects.filter(yVotes__gt=0)

So my end result would be when you browse to /admin page for VotedPost, it would only show posts that have more than 0 'Y' votes. 

Thanks in advance!