Where have I gone wrong in the Reply to Comments Views in Django

I am trying to add a reply to comments to posts in a blog, every time a reply is submitted it is added as a new comment not a reply although I have filtered comments to reply = None in the views.py

Here are models.py :

class Post(models.Model):
    title = models.CharField(max_length=100)
    likes = models.ManyToManyField(
        User, related_name='liked', blank=True)
    slug = models.SlugField(blank=True, null=True, max_length=120)

class Comment(models.Model):
    post = models.ForeignKey(
        Post, on_delete=models.CASCADE)
    user = models.ForeignKey(
        User, on_delete=models.CASCADE)
    reply = models.ForeignKey(
        'Comment', on_delete=models.CASCADE, null=True, related_name="replies")
    content = models.TextField(max_length=160)

Here are the views.py

class PostDetailView(DetailView):
    model = Post
    template_name = "post_detail.html"

    def get_context_data(self, *args, **kwargs):
        context = super(PostDetailView, self).get_context_data()
        post = get_object_or_404(Post, slug=self.kwargs['slug'])
        comments = Comment.objects.filter(
            post=post, reply=None).order_by('-id')
        total_likes = post.total_likes()
        liked = False
        if post.likes.filter(id=self.request.user.id).exists():
            liked = True

        if self.request.method == 'POST':
            comment_form = CommentForm(self.request.POST or None)
            if comment_form.is_valid():
                content = self.request.POST.get('content')
                reply_id = self.request.POST.get('comment_id')
                comment_qs = None

                if reply_id:
                    comment_qs = Comment.objects.get(id=reply_id)
                comment = Comment.objects.create(
                    post=post, user=request.user, content=content, reply=comment_qs)
                return HttpResponseRedirect("post_detail.html")
            comment_form = CommentForm()

        context["total_likes"] = total_likes
        context["liked"] = liked
        context["comments"] = comments
        context["comment_form"] = comment_form
        return context

class PostCommentCreateView(LoginRequiredMixin, CreateView):
    model = Comment
    form_class = CommentForm

    def form_valid(self, form):
        post = get_object_or_404(Post, slug=self.kwargs['slug'])
        form.instance.user = self.request.user
        form.instance.post = post
        return super().form_valid(form)

    def form_invalid(self, form):
        return HttpResponseRedirect(self.get_success_url())

    def get_success_url(self):
        return reverse('score:post-detail', kwargs=dict(slug=self.kwargs['slug']))

I have revised the views and I am not sure if I need to create a class-based view for the replied same as comments