Update constraints.

bikeshop_project/bike/models.py

@@ -78,7 +78,8 @@ class Bike(models.Model):
         return self.stolen is False and self.cpic_searched_at is not None and self.serial_number is not None
 
     def can_claim(self):
-        return self.claimed_by is None or self.last_worked_on > timezone.now() + timedelta(weeks=4)
+        return self.claimed_by is None or not (self.claimed_by is not None and self.last_worked_on > timezone.now() + timedelta(
+            weeks=4)) or self.last_worked_on is None
 
     def can_purchase(self):
         if self.claimed_by: