Fixed #20659 -- Fixed PublisherDetail in CBV topic documentation.

Thanks to tudor.prodan, susan, and Tim Graham for the report and reviews.

docs/topics/class-based-views/mixins.txt

@@ -286,18 +286,18 @@ One way to do this is to combine :class:`ListView` with
 for the paginated list of books can hang off the publisher found as the single
 object. In order to do this, we need to have two different querysets:
 
-``Publisher`` queryset for use in
-    :meth:`~django.views.generic.detail.SingleObjectMixin.get_object()`
-    We'll set the ``model`` attribute on the view and rely on the default
-    implementation of ``get_object()`` to fetch the correct ``Publisher``
-    object.
-
 ``Book`` queryset for use by :class:`~django.views.generic.list.ListView`
-    The default implementation of ``get_queryset()`` uses the ``model`` attribute
-    to construct the queryset. This conflicts with our use of this attribute
-    for ``get_object()`` so we'll override that method and have it return
-    the queryset of ``Book`` objects linked to the ``Publisher`` we're looking
-    at.
+    Since we have access to the ``Publisher`` whose books we want to list, we
+    simply override ``get_queryset()`` and use the ``Publisher``'s
+    :ref:`reverse foreign key manager<backwards-related-objects>`.
+
+``Publisher`` queryset for use in :meth:`~django.views.generic.detail.SingleObjectMixin.get_object()`
+    We'll rely on the default implementation of ``get_object()`` to fetch the
+    correct ``Publisher`` object.
+    However, we need to explicitly pass a ``queryset`` argument because
+    otherwise the default implementation of ``get_object()`` would call
+    ``get_queryset()`` which we have overridden to return ``Book`` objects
+    instead of ``Publisher`` ones.
 
 .. note::
 
@@ -317,12 +317,11 @@ Now we can write a new ``PublisherDetail``::
     from books.models import Publisher
 
     class PublisherDetail(SingleObjectMixin, ListView):
-        model = Publisher  # for SingleObjectMixin.get_object
         paginate_by = 2
         template_name = "books/publisher_detail.html"
 
         def get(self, request, *args, **kwargs):
-            self.object = self.get_object()
+            self.object = self.get_object(queryset=Publisher.objects.all())
             return super(PublisherDetail, self).get(request, *args, **kwargs)
 
         def get_context_data(self, **kwargs):