def rotation(new_rotation=0):
    """Set the display rotation.

    :param new_rotation: Specify the rotation in degrees: 0, 90, 180 or 270
    """

    global _rotation

    if new_rotation in [0, 90, 180, 270]:
        _rotation = new_rotation
        return True
    else:
        raise ValueError("Rotation: 0, 90, 180 or 270 degrees only")