code: def iss_spi_divisor(self, sck):
          
          _divisor = (6000000 / sck) - 1
          divisor = int(_divisor)
  
          if divisor != _divisor:
              raise ValueError('Non-integer SCK divisor.')
  
          if not 1 <= divisor < 256:
              error = (
                  "The value of sck_divisor, {}, "
                  "is not between 0 and 255".format(divisor)
              )
              raise ValueError(error)
          return divisor
docs: Calculate a USBISS SPI divisor value from the input SPI clock speed
  
          :param sck: SPI clock frequency
          :type sck: int
          :returns: ISS SCK divisor
          :rtype: int