old_contents: from django.conf.urls import url
  from helloworldapp import views
  
  urlpatterns = [
      url(r'^/$', views.helloworld),
  ]
  
new_contents: from django.conf.urls import url
  from helloworldapp import views
  
  urlpatterns = [
      url(r'^$', views.helloworld),
  ]
  
subject: Update urls.py