How to extract the vertices and indices from an SCNShape

Question

I am able to successfully create and SCNShape with the following command:

    let shape = SCNShape(path: path, extrusionDepth: 0)

where path is an NSBezierPath. I know this is successful because I can add it to an SCNNode and it draws successfully.

I would like to extract the vertices and indices of the elements. However, when I look at

shape.elements.first!.primitiveCount shape.sources.first!.vectorCount

after I create shape they are both equal to 0.

Is there a way to generate these so I can use them? Ultimately I want to use them to create a second custom shape.