docs: def get_urls(self):
          """
          Add our preview view to our urls.
          """
          urls = super(PageAdmin, self).get_urls()
          my_urls = patterns('',
              (r'^add/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
              (r'^(?P<id>\d+)/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
              (r'^(?P<id>\d+)/history/(\d+)/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
          )
          return my_urls + urls