  
  class Book(models.Model):
      name = models.CharField(max_length=100)
      authors = models.ManyToManyField(Author, related_name='books')
      publisher = models.ForeignKey(Publisher, related_name='books', db_column="publisher_id_column")
 
</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     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     author = models.ForeignKey(Author, related_name='books', null=True)
 </s> add     author = models.ForeignKey(Author, models.SET_NULL, related_name='books', null=True) </s> remove     author = models.ForeignKey(Author)
    book = models.ForeignKey(Book)
 </s> add     author = models.ForeignKey(Author, models.CASCADE)
    book = models.ForeignKey(Book, models.CASCADE)
    publisher = models.ForeignKey(
        Publisher,
        models.CASCADE,
        related_name='books',
        db_column="publisher_id_column",
    )
  
  class Book(models.Model):
      name = models.CharField(max_length=100)
      authors = models.ManyToManyField(Author, related_name='books')
    publisher = models.ForeignKey(
        Publisher,
        models.CASCADE,
        related_name='books',
        db_column="publisher_id_column",
    )
keep keep keep keep replace
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/get_or_create/models.py