      first_name = models.CharField(max_length=30)
      last_name = models.CharField(max_length=30)
      fun = models.BooleanField(default=False)
  
      favorite_book = models.ForeignKey('Book', null=True, related_name='favorite_books')
      favorite_thing_type = models.ForeignKey('contenttypes.ContentType', null=True)
      favorite_thing_id = models.IntegerField(null=True)
      favorite_thing = GenericForeignKey('favorite_thing_type', 'favorite_thing_id')
  
      objects = PersonManager()
      fun_people = FunPeopleManager()
 
</s> remove     favorite_book = models.ForeignKey('Book', null=True, related_name='fun_people_favorite_books')
    favorite_thing_type = models.ForeignKey('contenttypes.ContentType', null=True)
 </s> add     favorite_book = models.ForeignKey(
        'Book',
        models.SET_NULL,
        null=True,
        related_name='fun_people_favorite_books',
    )
    favorite_thing_type = models.ForeignKey('contenttypes.ContentType', models.SET_NULL, null=True) </s> remove     collection = models.ForeignKey(ProfileCollection, blank=True, null=True)
 </s> add     collection = models.ForeignKey(ProfileCollection, models.SET_NULL, blank=True, null=True) </s> remove     owner = models.ForeignKey(User, null=True, blank=True, on_delete=models.SET_NULL)
 </s> add     owner = models.ForeignKey(User, models.SET_NULL, null=True, blank=True) </s> remove     owner = models.ForeignKey(User)
 </s> add     owner = models.ForeignKey(User, models.CASCADE) </s> remove     store = models.ForeignKey(Store)
 </s> add     store = models.ForeignKey(Store, models.CASCADE)
    favorite_book = models.ForeignKey('Book', models.SET_NULL, null=True, related_name='favorite_books')
    favorite_thing_type = models.ForeignKey('contenttypes.ContentType', models.SET_NULL, null=True)
      first_name = models.CharField(max_length=30)
      last_name = models.CharField(max_length=30)
      fun = models.BooleanField(default=False)
  
    favorite_book = models.ForeignKey('Book', models.SET_NULL, null=True, related_name='favorite_books')
    favorite_thing_type = models.ForeignKey('contenttypes.ContentType', models.SET_NULL, null=True)
    favorite_book = models.ForeignKey('Book', models.SET_NULL, null=True, related_name='favorite_books')
    favorite_thing_type = models.ForeignKey('contenttypes.ContentType', models.SET_NULL, null=True)
      favorite_thing_id = models.IntegerField(null=True)
      favorite_thing = GenericForeignKey('favorite_thing_type', 'favorite_thing_id')
  
      objects = PersonManager()
      fun_people = FunPeopleManager()
keep keep keep keep replace replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/custom_managers/models.py