  class Article(models.Model):
      headline = models.CharField(max_length=100)
      pub_date = models.DateField()
      body = models.TextField(default='')
      reporter = models.ForeignKey(Reporter)
      response_to = models.ForeignKey('self', null=True)
  
      def __str__(self):
          return self.headline
  
      class Meta:
 
</s> remove     reporter = models.ForeignKey(Reporter)
    reporter_proxy = models.ForeignKey(ReporterProxy, null=True,
                                       related_name='reporter_proxy')
 </s> add     reporter = models.ForeignKey(Reporter, models.CASCADE)
    reporter_proxy = models.ForeignKey(
        ReporterProxy,
        models.SET_NULL,
        null=True,
        related_name='reporter_proxy',
    ) </s> remove     reporter = models.ForeignKey(Reporter, null=True)
 </s> add     reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True) </s> remove     primary_author = models.ForeignKey(Author, db_column='Author ID', related_name='primary_set', null=True)
 </s> add     primary_author = models.ForeignKey(
        Author,
        models.SET_NULL,
        db_column='Author ID',
        related_name='primary_set',
        null=True,
    ) </s> remove     parent = models.ForeignKey('self', null=True)
 </s> add     parent = models.ForeignKey('self', models.CASCADE, null=True) </s> remove     article = models.ForeignKey(Article, related_name="comments")
 </s> add     article = models.ForeignKey(Article, models.CASCADE, related_name="comments")
    reporter = models.ForeignKey(Reporter, models.CASCADE)
    response_to = models.ForeignKey('self', models.SET_NULL, null=True)
  class Article(models.Model):
      headline = models.CharField(max_length=100)
      pub_date = models.DateField()
      body = models.TextField(default='')
    reporter = models.ForeignKey(Reporter, models.CASCADE)
    response_to = models.ForeignKey('self', models.SET_NULL, null=True)
    reporter = models.ForeignKey(Reporter, models.CASCADE)
    response_to = models.ForeignKey('self', models.SET_NULL, null=True)
  
      def __str__(self):
          return self.headline
  
      class Meta:
keep keep keep keep replace replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/introspection/models.py