code: def sign(self, message, privkey, secret):
          
          m = self.GFn.value(message)
          x = self.GFn.value(privkey)
          k = self.GFn.value(secret)
  
          R = self.G * k
  
          r = self.GFn.value(R.x)
          s = (m + x * r) / k
  
          return (r, s)
docs: sign the message using private key and sign secret
          for signsecret k, message m, privatekey x
          return (G*k,  (m+x*r)/k)