python – 强制转换为Unicode：需要字符串或缓冲区,找到int – D

我正在使用Django Rest Framework来创建我自己的restful API,但是我收到了上面的错误,我不知道它来自哪里.我已经阅读了有关此错误的其他帖子,但不幸的是他们没有太多帮助,所以如果有人能指出我哪里出错了,我将不胜感激.当我在我的模型中创建一个AutoField时,它开始发生,它在Animal模型中标记,而不在Doctor中.

我的models.py：

# Create your models here.
class Doctor(models.Model):

    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=20)

    def __unicode__(self):
        return self.id

class Animal(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=200)
    gender = models.CharField(max_length=10,choices=GENDER)
    breed = models.CharField(max_length=200,)
    adoption = models.BooleanField(default=False)
    vaccines = models.CharField(max_length=20,choices=VACCINES)
    doctor = models.ForeignKey(Doctor,null=True)

    def __unicode__(self):
        return self.id

serialisers.py：

class DoctorSerealiser(serializers.HyperlinkedModelSerializer):
    class Meta:
         model = Doctor
         fields = ('id','name')


class AnimalSerialiser(serializers.HyperlinkedModelSerializer):

    # doctor = DoctorSerealiser(read_only=True)


    class Meta:
        model = Animal
        fields = ('id','name','gender','breed','adoption','vaccines','doctor')

views.py

class AnimalList(viewsets.ModelViewSet):
    queryset = Animal.objects.all()
    serializer_class = AnimalSerialiser

class DoctorDetail(viewsets.ModelViewSet):
    queryset = Doctor.objects.all()
    serializer_class = DoctorSerealiser

def __unicode__(self):
    return str(self.id)