code: def _get_plunger_position(self, position):
          
          try:
              value = self.plunger_positions[position]
              if helpers.is_number(value):
                  return value
              else:
                  raise RuntimeError(
                      'Plunger position "{}" not yet calibrated'.format(
                          position))
          except KeyError:
              raise RuntimeError(
                  'Plunger position "{}" does not exist'.format(
                      position))
docs: Returns the calibrated coordinate of a given plunger position
  
          Raises exception if the position has not been calibrated yet