Django Prefetch未获取相关字段

Question

我有四个引用CustomUser表的模型。

class Profile(models.Model):
    user = models.OneToOneField(CustomUser, on_delete=models.CASCADE)
    ...
class Question(models.Model):
    question = models.CharField(max_length=140)
class Answer(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE, related_name='answers')
    answer = models.CharField(max_length=70)
class Response(models.Model):
    user = models.ForeignKey(CustomUser, on_delete=models.CASCADE, related_name='responses')
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    answer = models.ForeignKey(Answer, on_delete=models.CASCADE)

每个问题都有多个答案，但每个用户只能为每个问题选择一个答案。

每个用户可以回答多个问题。

我有一个ViewSet，经身份验证的用户可以访问该ViewSet，该ViewSet应该返回具有与他们相同的答案的用户列表。

    serializer_class = serializers.ProfileSerializer
    def get_queryset(self):
        user_answers = qmodels.Answer.objects.filter(response__user=self.request.user)
        return models.Profile.objects.prefetch_related(
            Prefetch(
                'user__responses',
                queryset=qmodels.Response.objects.filter(answer__in=user_answers),
                to_attr='common_answers'
            )
        )

class ProfileSerializer(serializers.ModelSerializer):
    common_answers = ResponseSerializer(many=True)

但是，出现以下错误：

Got AttributeError when attempting to get a value for field `common_answers` on serializer `ProfileSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `Profile` instance.
Original exception text was: 'Profile' object has no attribute 'common_answers'.

我在prefetch_related之后添加了打印件，它可以正确显示基本记录，但是没有common_answers字段