          ordering = ('id',)
  
  
  class D(models.Model):
      b = models.ForeignKey(B, null=True)
  
      class Meta:
          ordering = ('id',)
  
  
 
</s> remove     b = models.ForeignKey(B)
 </s> add     b = models.ForeignKey(B, models.CASCADE) </s> remove     reporter = models.ForeignKey(Reporter, null=True)
 </s> add     reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True) </s> remove     z = models.ForeignKey('self')
 </s> add     z = models.ForeignKey('self', models.CASCADE) </s> remove     x = models.ForeignKey(LoopX)
 </s> add     x = models.ForeignKey(LoopX, models.CASCADE) </s> remove     owner = models.ForeignKey('Person', null=True)
    main_room = models.OneToOneField('Room', related_name='main_room_of', null=True)
 </s> add     owner = models.ForeignKey('Person', models.SET_NULL, null=True)
    main_room = models.OneToOneField('Room', models.SET_NULL, related_name='main_room_of', null=True)
    b = models.ForeignKey(B, models.SET_NULL, null=True)
          ordering = ('id',)
  
  
  class D(models.Model):
    b = models.ForeignKey(B, models.SET_NULL, null=True)
  
      class Meta:
          ordering = ('id',)
  
  
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/generic_relations_regress/models.py