old_contents: from django.conf.urls import url
  
  from . import views
  
  urlpatterns = [
      url(r'^$', views.index, name='index'),
  ]
new_contents: from django.conf.urls import url
  from . import views
  
  urlpatterns = [
      # ex: /polls/
      url(r'^$', views.index, name='index'),
      # ex: /polls/5/
      url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail'),
      # ex: /polls/5/results/
      url(r'^(?P<question_id>[0-9]+)/results/$', views.results, name='results'),
      # ex: /polls/5/vote/
      url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
  ]
subject: add url schema