def _get_sign(orientation, xaxis, yaxis):
    """ Helper to find multiplicative factors to get rotations right. """
    sign = {xaxis: 1, yaxis: 1}
    if orientation in ['left', 'bottom']:
        sign[xaxis] = 1
    else:
        sign[xaxis] = -1
    if orientation in ['right', 'bottom']:
        sign[yaxis] = 1
    else:
        sign[yaxis] = -1
    return sign
