Jo, tohle tedy nefunguje :(

seminar/models/tvorba.py

@@ -369,12 +369,6 @@ class Deadline(SeminarModelBase):
 	def __str__(self):
 		return self.CHOICES_MAP[self.typ] + " " + str(self.cislo)
 
-	def next(self):
-		return Deadline.objects.filter(gt=self).first()
-
-	def previous(self):
-		return Deadline.objects.filter(lt=self).last()
-
 
 
 @reversion.register(ignore_duplicates=True)