old_contents: from django.contrib import admin
  
  # Register your models here.
  from .models import Post
  
  admin.site.register(Post)
  
new_contents: from django.contrib import admin
  
  # Register your models here.
  from .models import Post
  
  
  class PostAdmin(admin.ModelAdmin):
      list_display = ('title', 'summary', 'created_at')
  
  
  admin.site.register(Post, PostAdmin)
  
subject: Update post admin. fix #16