code: def _select_ftdi_channel(channel):
      
      if channel < 0 or channel > 8:
          raise ArgumentError("FTDI-selected multiplexer only has channels 0-7 valid, "
                              "make sure you specify channel with -c channel=number", channel=channel)
      from pylibftdi import BitBangDevice
      bb = BitBangDevice(auto_detach=False)
      bb.direction = 0b111
      bb.port = channel
docs: Select multiplexer channel. Currently uses a FTDI chip via pylibftdi