  
  @python_2_unicode_compatible
  class Article(models.Model):
      headline = models.CharField(max_length=100)
      reporter = models.ForeignKey(Reporter, null=True)
  
      class Meta:
          ordering = ('headline',)
  
      def __str__(self):
 
</s> remove     reporter = models.ForeignKey(Reporter)
    response_to = models.ForeignKey('self', null=True)
 </s> add     reporter = models.ForeignKey(Reporter, models.CASCADE)
    response_to = models.ForeignKey('self', models.SET_NULL, null=True) </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     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     b = models.ForeignKey(B, null=True)
 </s> add     b = models.ForeignKey(B, models.SET_NULL, null=True) </s> remove     item = models.ForeignKey(Item)
 </s> add     item = models.ForeignKey(Item, models.CASCADE)
    reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True)
  
  @python_2_unicode_compatible
  class Article(models.Model):
      headline = models.CharField(max_length=100)
    reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True)
  
      class Meta:
          ordering = ('headline',)
  
      def __str__(self):
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/many_to_one_null/models.py