Straight Skeleton from concave polygon in CGAL

I have a collection of concave and simple polygons. see image below:

However, CGAL reports these polygons as complex.

I'm using a python library as a wrapper for CGAL, its scikit-geometry

poly.is_simple() #False  

And the CGAL throws this, "The input polygon is not simple.", error when running:

skel = sg.skeleton.create_interior_straight_skeleton(poly)  

As far as I'm aware these polygons are all simple, they do not intersect themselves anywhere. Am I mistaken in my definition of "Simple" and if so, how would I get the straight skeleton for these polygons even if they are complex?

https://stackoverflow.com/questions/65622468/straight-skeleton-from-concave-polygon-in-cgal January 08, 2021 at 10:05AM