Convenience shift+rotate combination.

def pts_relative(pts=[], shift=[0.0, 0.0], angle=[0.0]):
    '''Convenience shift+rotate combination.
    '''
    assert isinstance(pts, list) and len(pts) > 0
    l_pt_prev = None
    for pt in pts:
        assert isinstance(pt, tuple)
        l_pt = len(pt)
        assert l_pt > 1
        for i in pt:
            assert isinstance(i, float)
        if l_pt_prev is not None:
            assert l_pt == l_pt_prev
        l_pt_prev = l_pt
    assert isinstance(shift, list)
    l_sh = len(shift)
    assert l_sh == l_pt
    for i in shift:
        assert isinstance(i, float)
    assert isinstance(angle, list)
    l_angle = len(angle)
    assert l_angle == l_pt-1
    for i in angle:
        assert isinstance(i, float)
        assert abs(i) <= 2*pi

    return [pt_relative(pt, shift, angle) for pt in pts]