Maintain the parent ID in the querystring for response_add and
        response_change.

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