old_contents: 
  from django.contrib import admin
  from mezzanine.core.admin import DisplayableAdmin
  from .models import Link
  
  
  class LinkAdmin(DisplayableAdmin):
      list_display = ("id", "title", "status", "publish_date",
                      "user", "comments_count", "rating_sum")
      list_display_links = ("id",)
      list_editable = ("title", "status")
      list_filter = ("status", "user__username")
      ordering = ("-publish_date",)
  
  
  admin.site.register(Link, LinkAdmin)
  
new_contents: 
  from django.contrib import admin
  from mezzanine.core.admin import DisplayableAdmin
  from .models import Link
  
  
  class LinkAdmin(DisplayableAdmin):
  
      list_display = ("id", "title", "link", "status", "publish_date",
                      "user", "comments_count", "rating_sum")
      list_display_links = ("id",)
      list_editable = ("title", "link", "status")
      list_filter = ("status", "user__username")
      ordering = ("-publish_date",)
  
      fieldsets = (
          (None, {
              "fields": ("title", "link", "status", "publish_date", "user"),
          }),
      )
  
  
  admin.site.register(Link, LinkAdmin)
  
subject: Fix link admin fieldsets. Closes #3.