我有以下 django 型號：

class Listing(models.Model)
    STATUS_CHOICES = [
        ('available', 'Available'),
        ('rented', 'Rented'),
        ('unavailable', 'Unavailable'),
        ('fake', 'Fake'),
    ]

    id = models.AutoField(primary_key=True)
    title = models.CharField(max_length=200)
    description = models.TextField()
    status = models.CharField(max_length=12, choices=STATUS_CHOICES, default='available')
    def save(self, *args, **kwargs):
        ## 
        if self.status == 'fake' and  ......:
            raise PermissionDenied("Cannot save listing with