Update docs imports (#7030)

docs/api-guide/caching.md

@@ -17,11 +17,16 @@ other cache decorators such as [`cache_page`][page] and
 [`vary_on_cookie`][cookie].
 
 ```python
+from django.utils.decorators import method_decorator
+from django.views.decorators.cache import cache_page
+from django.views.decorators.vary import vary_on_cookie
+
 from rest_framework.response import Response
 from rest_framework.views import APIView
 from rest_framework import viewsets
 
-class UserViewSet(viewsets.Viewset):
+
+class UserViewSet(viewsets.ViewSet):
 
     # Cache requested url for each user for 2 hours
     @method_decorator(cache_page(60*60*2))
@@ -32,6 +37,7 @@ class UserViewSet(viewsets.Viewset):
         }
         return Response(content)
 
+
 class PostView(APIView):
 
     # Cache page for the requested url