def _get_plunger_position(self, position):
        """
        Returns the calibrated coordinate of a given plunger position

        Raises exception if the position has not been calibrated yet
        """
        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))
Returns the calibrated coordinate of a given plunger position

        Raises exception if the position has not been calibrated yet