wrong url in document of horizon tutorial

[Canh Truong]

I follow the steps in tutorial "Adding a complex action to a table" and I get the error when run again horizon:

Error reversing absolute URL for <Panel: mypanel>: Reverse for 'index' with arguments '()' and keyword arguments '{}' not found. 0 pattern(s) tried: []
Internal Server Error: /admin/
Traceback (most recent call last):
  File "/opt/stack/horizon/.venv/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 137, in get_response
    response = response.render()
  File "/opt/stack/horizon/.venv/local/lib/python2.7/site-packages/django/template/response.py", line 103, in render
    self.content = self.rendered_content
  File "/opt/stack/horizon/.venv/local/lib/python2.7/site-packages/django/template/response.py", line 80, in rendered_content
    content = template.render(context)
  File "/opt/stack/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 148, in render
    return self._render(context)
...
   (lookup_view_s, args, kwargs, len(patterns), patterns))
NoReverseMatch: Reverse for 'index' with arguments '()' and keyword arguments '{}' not found. 0 pattern(s) tried: []

The url pattern is wrong. Change it as :
urlpatterns = patterns('',
    url(r'^$',
        views.IndexView.as_view(), name='index'),
    url(r'^(?P<instance_id>[^/]+)/create_snapshot/$',
        views.CreateSnapshotView.as_view(),
        name='create_snapshot'),
)
is okei.

Tutorial at: http://docs.openstack.org/developer/horizon/topics/table_actions.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/185346

[Johan Öhman Saldes (josal)]

urlpatterns = [,
    url(r'^$',
        views.IndexView.as_view(), name='index'),
    url(r'^(?P<instance_id>[^/]+)/create_snapshot/$',
        views.CreateSnapshotView.as_view(),
        name='create_snapshot'),
]

Still gives an error for me? I removed the comma as such:

urlpatterns = [
    url(r'^$',
        views.IndexView.as_view(), name='index'),
    url(r'^(?P<instance_id>[^/]+)/create_snapshot/$',
        views.CreateSnapshotView.as_view(),
        name='create_snapshot'),
]

And it worked!