Run to a position relative to the current `position` value.
        The new position will be current `position` + `position_sp`.
        When the new position is reached, the motor will stop using
        the action specified by `stop_action`.

def run_to_rel_pos(self, **kwargs):
        """
        Run to a position relative to the current `position` value.
        The new position will be current `position` + `position_sp`.
        When the new position is reached, the motor will stop using
        the action specified by `stop_action`.
        """
        for key in kwargs:
            setattr(self, key, kwargs[key])
        self.command = self.COMMAND_RUN_TO_REL_POS