old_contents: from django.contrib import admin
  
  # Register your models here.
  
new_contents: from django.contrib import admin
  
  from models import Author, Comment, Post
  # Register your models here.
  
  
  admin.site.register(Post)
  admin.site.register(Comment)
  admin.site.register(Author)
  
  admin.site.unregister(Author)
subject: add some admin registration.