old_contents: from django.conf.urls import url
  from app.views import StemView
  from rest_framework.urlpatterns import format_suffix_patterns
  
  urlpatterns = [
          url(r'^stem/$', StemView.as_view()),
          ]
  
  urlpatterns += format_suffix_patterns(urlpatterns)
  
new_contents: from django.conf.urls import url
  from app.views import StemView
  from rest_framework.urlpatterns import format_suffix_patterns
  
  urlpatterns = [
          url(r'^api/stem/$', StemView.as_view()),
          ]
  
  urlpatterns += format_suffix_patterns(urlpatterns)
  
subject: update url