Group: V 2.36 release
Add a mesh, create groups in it, using the API add vertex to it, I copy the ones from a group, update the mesh, the script ends without error or warning, then try to edit the mesh, and blender hangs.
If the line in the script with comment is commented, blender isn't hanged.
P.S. i've discovered this trying to do a script for the extrude operation that isn't in the API.