python - Django ModelSerializer 如何POST提交非Models中定义、关联表中的字段？

我在用djangorestframwork框架为app客户端提供接口，现在遇到个问题如下，IWannaImages表外键IWanna表，现在我通过接口POST提交IWanna数据的时候无法获取客户端POST过来的到关联表IwannaImages的信息

这是我打印的客户端提交的数据validated_data的内容：

{u'platform': u'ios', u'reason': u'\u5b81\u65e5\u8363\u6e7f\u7b54\u7b54\u53d1\u751f\u7684\u53d1\u7ed9\u6211\u7684', u'error_type': u'\u8f6f\u4ef6\u9519\u8bef', u'user_id': 56, u'wanna_type': u'\u7ea0\u9519\u8bef'}

从打印结果来看后台就没接收到客户端传递的images的数据，感觉是serializer这块不对，接口这块该如何处理呢？

models.py

class IWanna(models.Model):
    wanna_type = models.CharField(max_length=32, verbose_name=_("I wanna type"))
    scene_name = models.CharField(max_length=128, null=True, blank=True, verbose_name=_("scene name"))
    city_name = models.CharField(max_length=128, null=True, blank=True, verbose_name=_("city name"))
    reason = models.TextField(null=True, blank=True, verbose_name=_("wanna reason"))
    user_id = models.IntegerField(verbose_name=_("user id"))
    platform = models.CharField(max_length=32, verbose_name=_("platform"))
    error_type = models.CharField(max_length=128, null=True, blank=True, verbose_name=_("error type"))
    image = models.ImageField(upload_to=wanna_image_upload_to, null=True, blank=True, verbose_name=_("image"))
    improve_type = models.CharField(max_length=32, null=True, blank=True, verbose_name=_("improve type"))

    class Meta:
        app_label = 'people'
        verbose_name = _("I Wanna")
        verbose_name_plural = _("I Wanna")

    def __unicode__(self):
        return "{}-{}".format(self.id, self.wanna_type)


class IWannaImages(models.Model):
    iwanna = models.ForeignKey("IWanna", related_name="images", verbose_name=_("i wanna type"))
    image = models.ImageField(upload_to=wanna_image_upload_to, verbose_name=_("image"))

serializers.py

class IWannaSerializer(serializers.ModelSerializer):
    images = serializers.SerializerMethodField()

    class Meta:
        model = IWanna
        fields = (
            "id", "wanna_type", "scene_name", "city_name", "reason", "user_id",
            "platform", "error_type", "images", "improve_type", "image"
        )
        depth = 1

    def validate(self, attrs):
        if attrs["platform"] not in ["ios", "android"]:
            raise ValidationError({"platform": "platform not allowed"})
        return attrs

    def get_images(self, instance):
        data = IWannaImageSerializer(instance.images, many=True).data
        return data

    def create(self, validated_data):
        instance = super(IWannaSerializer, self).create(validated_data)
        try:
            if validated_data["images"]:   # traverse images from app
                for i in validated_data["images"]:
                    IWannaImages.objects.create(iwanna=instance, image=i)
        except Exception, e:
            import logging
            logging.warn(e.message)
        return instance