docs: def get_unread(self, request, notifications, mark_as_read):
          """
          return unread notifications and mark as read
          (unless read=false param is passed)
          """
          notifications = notifications.filter(is_read=False)
          serializer = UnreadNotificationSerializer(list(notifications),  # evaluate queryset
                                                    many=True,
                                                    context=self.get_serializer_context())
          # retrieve unread notifications as read (default behaviour)
          if mark_as_read:
              notifications.update(is_read=True)
          return Response(serializer.data)