offset_points function returns none

[Gadgeteering]

When executing the offset point command below with the following shape None is returned.

shape = [(60.007, 5.054), (58.407, 5.054), (58.407, 5.054), (58.407, 3.655), (58.407, 3.655), (60.007, 3.655), (60.007, 3.655), (60.007, 5.054)]
offset = 0.1
inside=False
utils.offset_points(shape, offset, internal=inside)

[None, None, None, None, None, None, None, None]