title: including extra context value django rest framework
body: <p>I am using django rest framework. I need to pass some extra context value in response but not getting extra_value in response.</p>
  
  <pre><code>class ResultRowView(generics.ListAPIView):
      serializer_class    = ResultRowSerializer
      permission_classes  = (AccountPermission, )
  
      def get_serializer(self, *args, **kwargs):
          context = {'extra_value': 5000}
          return self.serializer_class(*args, context=context, **kwargs)
  
      def get_queryset(self):
          qs = ResultRow.objects.none()
          pk = self.kwargs.get('pk', None)
          try:
              route = IncomingRoute.objects.get(account=self.request.user.account, pk=pk)
              qs = route.app_module.rows.all()
          except Exception, e:
              print 'result_row_query: ', e
          return qs
  </code></pre>
  
  <p>What is missing here ?</p>