old_contents: from django.contrib import admin
  from polymorphic.admin import PolymorphicParentModelAdmin, PolymorphicChildModelAdmin
  from .models import WallPost, MediaWallPost, TextWallPost
  
  
  class MediaWallPostAdmin(PolymorphicChildModelAdmin):
      base_model = WallPost
  
  
  class TextWallPostAdmin(PolymorphicChildModelAdmin):
      base_model = WallPost
  
  
  class WallPostParentAdmin(PolymorphicParentModelAdmin):
      """ The parent model admin """
      base_model = WallPost
      child_models = (
          (MediaWallPost, MediaWallPostAdmin),
          (TextWallPost, TextWallPostAdmin),
      )
  
  # Only the parent needs to be registered:
  admin.site.register(WallPost, WallPostParentAdmin)
new_contents: from django.contrib import admin
  from polymorphic.admin import PolymorphicParentModelAdmin, PolymorphicChildModelAdmin
  from .models import WallPost, MediaWallPost, TextWallPost
  
  
  class MediaWallPostAdmin(PolymorphicChildModelAdmin):
      base_model = WallPost
  
  
  class TextWallPostAdmin(PolymorphicChildModelAdmin):
      base_model = WallPost
  
  
  class WallPostParentAdmin(PolymorphicParentModelAdmin):
      """ The parent model admin """
      base_model = WallPost
      child_models = (
          (MediaWallPost, MediaWallPostAdmin),
          (TextWallPost, TextWallPostAdmin),
      )
  
  # Only the parent needs to be registered:
  admin.site.register(WallPost, WallPostParentAdmin)
  
subject: Add newline to admin.py.