      from geography.models import ZipCode
  
      class Restaurant(models.Model):
          # ...
          zip_code = models.ForeignKey(ZipCode)
  
  Field name restrictions
  -----------------------
  
  Django places only two restrictions on model field names:
 
</s> remove         manufacturer = models.ForeignKey(Manufacturer)
 </s> add         manufacturer = models.ForeignKey(Manufacturer, on_delete=models.CASCADE) </s> remove         kind = models.ForeignKey(ThingKind, related_name='kinds',
                                 verbose_name=_('kind'))
 </s> add         kind = models.ForeignKey(
            ThingKind,
            on_delete=models.CASCADE,
            related_name='kinds',
            verbose_name=_('kind'),
        )
        zip_code = models.ForeignKey(
            ZipCode,
            on_delete=models.SET_NULL,
            blank=True,
            null=True,
        )
      from geography.models import ZipCode
  
      class Restaurant(models.Model):
          # ...
        zip_code = models.ForeignKey(
            ZipCode,
            on_delete=models.SET_NULL,
            blank=True,
            null=True,
        )
  
  Field name restrictions
  -----------------------
  
  Django places only two restrictions on model field names:
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
docs/topics/db/models.txt