如何在graphene django中添加数据库中不存在的自定义字段

from django.db import models

class MyModel(models.Model):
    # 其他字段...
    custom_field = models.CharField(max_length=100)

import graphene

class MyModelType(graphene.ObjectType):
    # 其他字段...
    custom_field = graphene.String()

    def resolve_custom_field(self, info):
        return self.custom_field

class Query(graphene.ObjectType):
    my_model = graphene.Field(MyModelType)

    def resolve_my_model(self, info):
        # 获取数据库中的模型实例
        my_model_instance = MyModel.objects.first()
        return my_model_instance

query {
  myModel {
    customField
  }
}