为什么django rest框架不显示OneToOneField数据-django

我想在我的网站上设置restful API。我使用了django rest框架。

class Profile(models.Model):
    user = models.OneToOneField(settings.AUTH_USER_MODEL, related_name='profile',on_delete=models.CASCADE)
    name = models.CharField(max_length=30)
    family = models.CharField(max_length=50)

下面是我的第二个模型(子模型):

class Klass(models.Model):
    title = models.CharField(max_length=50)
    description = models.CharField(max_length=500)
    teacher = models.ForeignKey(Profile,related_name='teacher', on_delete=models.CASCADE)
    university = models.CharField(max_length=50, blank=True, null=True)

teacher Profile 模型

pk .

# serializer
class KlassSerializer(serializers.ModelSerializer):

    class Meta:
        model = Klass
        fields = ('id', 'title', 'description', 'teacher')

# view
class KlassView(APIView):

    def get(self, request, pk=None):
        if pk is not None:
            klass = Klass.objects.filter(pk=pk).get()
            serializer = KlassSerializer(klass)
            return Response({'message': 'class get ', 'data': serializer.data,})

结果如下:

{
    "message": "class get ",
    "data": {
        "id": 13,
        "title": "ُThe First Class",
        "description": "Nothing for now!",
        "teacher": 2
    }
}

我怎样才能解决这个问题? 谢谢