code: def set_default(self, channels=None):
          '''Setting default voltage
          '''
          if not channels:
              channels = self._ch_cal.keys()
          for channel in channels:
              self.set_voltage(channel, self._ch_cal[channel]['default'], unit='V'f set_default(self, channels=None):
          '''Setting default voltage
          '''
          if not channels:
              channels = self._ch_cal.keys()
          for channel in channels:
              self.set_voltage(channel, self._ch_cal[channel]['default'], unit='V')
docs: Setting default voltage