how to deal with model property in django view

Question

I am trying to do an ecommerce app ,where in i have to add coupon code in the checkout page. I had a model property to check for the coupon code validity.Here is my code

model:

class CoupenCode(models.Model):
code=models.CharField(max_length=100)
startdate=models.DateField()
enddate=models.DateField()
discount=models.IntegerField()
disc_type=models.CharField(max_length=20,choices=(
    ('Amount','Amount'),
    ('Percentage','Percentage')))
usercount=models.PositiveIntegerField()
min_amount=models.PositiveIntegerField()

@property
def is_expired(self):
    if datetime.now().date() > self.enddate or datetime.now().date() < self.startdate :
        return False
    return True

class Meta:
    db_table = 'CoupenCode'
    ordering = ['-id']

def __str__(self):
    return self.code

views:

def fncoupon(request):
if request.method=="POST":
    coupon=request.POST.get('promo')
    couponcode=CoupenCode.objects.filter(code=coupon)
    validity=couponcode.is_expired()
    if validity == True :
        if couponcode.disc_type == "Amount":
            discount=couponcode.discount + 'Rs'
        else:
            discount=couponcode.discount + '%'
        print(discount)
        return JsonResponse({'discount':discount})

    else:
        message="This coupon code is not valid"

    print(message)
    return JsonResponse({'message':message})

the problem is i cant check for the coupon code validity using this property in views.it gives me an error

'QuerySet' object has no attribute 'is_expired'

Can anyone please suggest me how i could solve this..