  
  
  @python_2_unicode_compatible
  class ObjectReference(models.Model):
      obj = models.ForeignKey(Object, db_constraint=False)
  
      def __str__(self):
          return str(self.obj_id)
  
  
 
</s> remove     plot = models.OneToOneField(Plot)
 </s> add     plot = models.OneToOneField(Plot, models.CASCADE) </s> remove     network = models.ForeignKey(Network)
 </s> add     network = models.ForeignKey(Network, models.CASCADE) </s> remove     poet = models.ForeignKey(Poet)
 </s> add     poet = models.ForeignKey(Poet, models.CASCADE) </s> remove     two = models.ForeignKey('CyclicTwo')
 </s> add     two = models.ForeignKey('CyclicTwo', models.CASCADE) </s> remove     one = models.ForeignKey(CyclicOne)
 </s> add     one = models.ForeignKey(CyclicOne, models.CASCADE)
    obj = models.ForeignKey(Object, models.CASCADE, db_constraint=False)
  
  
  @python_2_unicode_compatible
  class ObjectReference(models.Model):
    obj = models.ForeignKey(Object, models.CASCADE, db_constraint=False)
  
      def __str__(self):
          return str(self.obj_id)
  
  
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/backends/models.py