code: def get_set_voltage(self, channel):
          
          ret = self.ask("V%d?" % channel)
          if ret[:3] != "V%d " % channel:
              print("ttiQl355tp.get_voltage() format error", ret)
              return None
          return float(ret[3:])
docs: channel: 1=OP1, 2=OP2, AUX is not supported