urls.pyでNameError: name 'polls' is not defined

Djangoのチュートリアルの学習中なのですが、urls.pyを編集後、
runserverコマンドをたたくと、

NameError: name 'polls' is not defined

となり起動できません。

以下、ソースです。

python
1  2 
2  3 The `urlpatterns` list routes URLs to views. For more information please see:
3  4     https://docs.djangoproject.com/en/1.11/topics/http/urls/
4  5 Examples:
5  6 Function views
6  7     1. Add an import:  from my_app import views
7  8     2. Add a URL to urlpatterns:  url(r'^$', views.home, name='home')
8  9 Class-based views
9 10     1. Add an import:  from other_app.views import Home
10 11     2. Add a URL to urlpatterns:  url(r'^$', Home.as_view(), name='home')
11 12 Including another URLconf
12 13     1. Import the include() function: from django.conf.urls import url, include
13 14     2. Add a URL to urlpatterns:  url(r'^blog/', include('blog.urls'))
14 15 """
15 16 from django.conf.urls import include, url
16 17 from django.contrib import admin
17 18 from item.views import home
18 19 
19 20 urlpatterns = [
20 21     url(r'^admin/', admin.site.urls),
21 22     url(r'^$', home, name='home'),
22 23     url(r'^polls/', include(polls.urls, namespace='polls')),
23 24 ]
24