Find the related model & serialize it back

        If the parent resource of the related model doesn't
        exist then abort on a 404.

def on_get(self, req, resp, rid, related):
        """ Find the related model & serialize it back

        If the parent resource of the related model doesn't
        exist then abort on a 404.
        """

        signals.pre_req.send(self.model)
        signals.pre_req_find.send(self.model)

        if not hasattr(self.model, related):
            abort(InvalidURL(**{
                'detail': 'The "%s" resource does not have a related '
                          'resource named "%s". This is an error, check '
                          'your spelling & retry.' % (self.rtype, related)
            }))

        model = find(self.model, rid)
        try:
            model_related = getattr(model, related).load()
        except AttributeError:
            model_related = None

        if isinstance(model_related, list):
            props = to_rest_models(model_related, includes=req.includes)
        elif model:
            props = to_rest_model(model_related, includes=req.includes)
        else:
            props = model_related

        resp.serialize(props)

        signals.post_req.send(self.model)
        signals.post_req_find.send(self.model)