title: order by method is not working on queryset
body: <p>order by  not working on queryset  no working at all and i dont know where is the mistake seems everything is okay !</p>
  <p>views.py</p>
  <pre><code>class PostDetailView(DetailView):
  model = Post
  template_name = 'detail.html'
  #context_object_name = 'post'
  #form_class = CommentForm
  
  def get_context_data(self, **kwargs):
      data = super().get_context_data(**kwargs)
  
      post_comments = Comment.objects.filter(post=self.get_object()).order_by('-date_added')
      data['comments'] = post_comments
  
      if self.request.user.is_authenticated:
          data['comment_form'] = CommentForm(instance=self.request.user)
      return data
  
  def post(self, request, slug, *args, **kwargs):
      new_comment = Comment(comment=request.POST.get('comment'),
                              name = self.request.user,
                              post = self.get_object())
      new_comment.save()
      return redirect('core:detail', slug=slug)
  </code></pre>
  <p>models.py</p>
  <pre><code>class Comment(models.Model):
  post = models.ForeignKey(Post, related_name='comments', on_delete=models.CASCADE)
  name = models.ForeignKey(User, on_delete=models.CASCADE)
  comment = models.TextField()
  date_added = models.DateTimeField(auto_now_add=True)
  
  def __str__(self):
      return self.comment
  </code></pre>