      pages = models.IntegerField()
      rating = models.FloatField()
      price = models.DecimalField(decimal_places=2, max_digits=6)
      authors = models.ManyToManyField(Author)
      contact = models.ForeignKey(Author, related_name='book_contact_set')
      publisher = models.ForeignKey(Publisher)
      pubdate = models.DateField()
      tags = GenericRelation(ItemTag)
  
      class Meta:
          ordering = ('name',)
 
</s> remove     contact = models.ForeignKey(Author, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher)
 </s> add     contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher, models.CASCADE) </s> remove     contact = models.ForeignKey(Author, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher)
 </s> add     contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher, models.CASCADE) </s> remove     band = models.ForeignKey(Band)
 </s> add     band = models.ForeignKey(Band, models.CASCADE) </s> remove     author = models.ForeignKey(Author, to_field='name', related_name='i_like')
    likes_author = models.ForeignKey(Author, to_field='name', related_name='likes_me')
 </s> add     author = models.ForeignKey(Author, models.CASCADE, to_field='name', related_name='i_like')
    likes_author = models.ForeignKey(Author, models.CASCADE, to_field='name', related_name='likes_me') </s> remove     creator = models.ForeignKey(Author)
    note = models.ForeignKey(Note)
 </s> add     creator = models.ForeignKey(Author, models.CASCADE)
    note = models.ForeignKey(Note, models.CASCADE)
    contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher, models.CASCADE)
      pages = models.IntegerField()
      rating = models.FloatField()
      price = models.DecimalField(decimal_places=2, max_digits=6)
      authors = models.ManyToManyField(Author)
    contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher, models.CASCADE)
    contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set')
    publisher = models.ForeignKey(Publisher, models.CASCADE)
      pubdate = models.DateField()
      tags = GenericRelation(ItemTag)
  
      class Meta:
          ordering = ('name',)
keep keep keep keep replace replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/aggregation_regress/models.py