code: def Hi(self, str_, salt, i):
          
          # pylint: disable=C0103
          Uj = self.HMAC(str_, salt + b"\000\000\000\001") # U1
          result = Uj
          for _ in range(2, i + 1):
              Uj = self.HMAC(str_, Uj)               # Uj = HMAC(str, Uj-1)
              result = self.XOR(result,  Uj)         # ... XOR Uj-1 XOR Uj
          return result
docs: The Hi(str, salt, i) function.