如何拥有一个包含四个表的Django关系数据库？

我正在使用Django创建一个网站，并且数据库存在问题！我有四个表（主题，问题，答案和图像）。这些表中的每一个都有一个id列，我想将这四个表连接在一起。

我试过使用ForeignKey()但是没有用。我收到一条错误消息。我不知道我是否可以ManyToManyField()在这种情况下使用，因为我只想连接一列。

这是代码：

from django.db import models

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

topic_id = models.AutoField(primary_key=True)
topic_level = models.BooleanField()
topic_name = models.TextField()

class questions(models.Model):

question_id = models.AutoField(primary_key=True)
description = models.TextField()
questions_type = models.BooleanField()

class answers(models.Model):

answer_id = models.AutoField(primary_key=True)
description = models.TextField()

class images (models.Model):

image_id = models.AutoField(primary_key=True)
image_blob = models.BinaryField()

这是代码ForeignKey()：

from django.db import models

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

topic_id = models.AutoField(primary_key=True)
topic_level = models.BooleanField()
topic_name = models.TextField()
topic_question = models.ForeignKey(questions, on_delete=CASCADE)
topic_answer = models.ForeignKey(answers, on_delete=CASCADE)
topic_image = models.ForeignKey(images, on_delete=CASCADE)

class questions(models.Model):

question_id = models.AutoField(primary_key=True)
description = models.TextField()
questions_type = models.BooleanField()
question_topic = models.ForeignKey(topics, on_delete=CASCADE)
question_answer = models.ForeignKey(answers, on_delete=CASCADE)
question_image = models.ForeignKey(images, on_delete=CASCADE)

class answers(models.Model):

answer_id = models.AutoField(primary_key=True)
description = models.TextField()
answer_topic = models.ForeignKey(topics, on_delete=CASCADE)
answer_question = models.ForeignKey(questions, on_delete=CASCADE)
answer_image = models.ForeignKey(images, on_delete=CASCADE)

class images (models.Model):

image_id = models.AutoField(primary_key=True)
image_blob = models.BinaryField()
image_topic = models.ForeignKey(topics, on_delete=CASCADE)
image_question = models.ForeignKey(questions, on_delete=CASCADE)
image_answer= models.ForeignKey(answers, on_delete=CASCADE)

这是我收到的错误消息：

topic_question = models.ForeignKey（questions，on_delete = CASCADE）NameError：名称'问题'未定义