          return repr(self.pk)
  
  
  class Foo(models.Model):
      bar = models.ForeignKey(Bar)
 
</s> remove     item = models.ForeignKey(Item)
 </s> add     item = models.ForeignKey(Item, models.CASCADE) </s> remove     item = models.ForeignKey(SimpleItem)
 </s> add     item = models.ForeignKey(SimpleItem, models.CASCADE) </s> remove     content_type = models.ForeignKey(ContentType)
 </s> add     content_type = models.ForeignKey(ContentType, models.CASCADE) </s> remove     retailer = models.ForeignKey(Supplier, related_name='wholesale_supplier')
 </s> add     retailer = models.ForeignKey(Supplier, models.CASCADE, related_name='wholesale_supplier') </s> remove     city = models.ForeignKey(City)
 </s> add     city = models.ForeignKey(City, models.CASCADE)
    bar = models.ForeignKey(Bar, models.CASCADE)
          return repr(self.pk)
  
  
  class Foo(models.Model):
    bar = models.ForeignKey(Bar, models.CASCADE)
keep keep keep keep replace
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/custom_pk/models.py