Hi Savya,
I tried something like this:
def _generate_sign(self):
signaturekey = 'signature',
MerchantID= 'MID',
u_reference= 'reference',
u_amount= 'amount',
u_currency= 'currency',
key = str("%s;%s;%s;%s;%s" % (signaturekey, MerchantID, u_reference, u_amount, u_currency))
shasign = sha512(key.encode('utf-8')).hexdigest()
return shasign

I get the following error:
Server Error:
We are not able to redirect you to the payment form. _generate_sign() takes 1 positional argument but 3 were given

I'm not sure if I'm doing the right thing.