def tweak(positioner, step):
    positioner=to_list(string_to_obj(positioner))
    step = to_list(step)
    while (True):
        key=get_context().waitKey(0)
        if key == 0x25 : #Left
            for i in range(len(positioner)):
                positioner[i].moveRel(-step[i])
        elif key == 0x27 : #Right
            for i in range(len(positioner)):
                positioner[i].moveRel(step[i])