Return given points scaled by factor f from origin.

def pts_scale(pts=[], f=1.0):
    '''Return given points scaled by factor f from origin.
    '''
    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(f, float)

    return [pt_scale(pt, f) for pt in pts]