docs: def _maintain_parent(self, request, response):
          """
          Maintain the parent ID in the querystring for response_add and
          response_change.
          """
          location = response._headers.get("location")
          parent = request.GET.get("parent")
          if parent and location and "?" not in location[1]:
              url = "%s?parent=%s" % (location[1], parent)
              return HttpResponseRedirect(url)
          return response