code: def _volume_percentage(self, volume):
          
          if volume < 0:
              raise RuntimeError(
                  "Volume must be a positive number, got {}.".format(volume))
          if volume > self.max_volume:
              raise RuntimeError(
                  "{0}µl exceeds pipette's maximum volume ({1}ul).".format(
                      volume, self.max_volume))
          if volume < self.min_volume:
              self.robot.add_warning(
                  "{0}µl is less than pipette's min_volume ({1}ul).".format(
                      volume, self.min_volume))
  
          return volume / self.max_volume
docs: Returns the plunger percentage for a given volume.
  
          We use this to calculate what actual position the plunger axis
          needs to be at in order to achieve the correct volume of liquid.