如何在django中从单个字段的多个模型创建外键

from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType

class ModelA(models.Model):
    # 其他字段
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')

class ModelB(models.Model):
    # 其他字段
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')

class ModelC(models.Model):
    # 其他字段
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')

model_b_instance = ModelB.objects.get(id=1)
model_a_instance = ModelA.objects.create(content_object=model_b_instance)