replace if-cases to annotate

fet2020/posts/views.py

@@ -250,11 +250,7 @@ def __next(post=None, public=True):
     d = post.slug
 
     if post:
-        # TODO: bad implementation but it works!!
-        if post.post_type == "N" or post.post_type == "E":
-            posts = Post.articles.date_sorted_list(public)
-        elif post.post_type == "F":
-            posts = FetMeeting.objects.published(public)
+        posts = Post.objects.date_sorted_list(public).filter(post_type=post.post_type)
 
     if posts:
         for k, v in enumerate(posts):