old_contents: from django.contrib import admin
  from django.contrib.auth.admin import UserAdmin
  from django.contrib.auth.models import User
  
  from django_sloop.admin import SloopAdminMixin
  from test_app.devices.models import Device
  
  
  class CustomUserAdmin(SloopAdminMixin, UserAdmin):
      actions = ("send_push_notification", )
  
  
  admin.site.unregister(User)
  admin.site.register(User, CustomUserAdmin)
  admin.site.register(Device)
  
new_contents: from django.contrib import admin
  from test_app.devices.models import Device
  
  admin.site.register(Device)
  
subject: remove unused codes