fromNative Layers do not have the property 'type'
Use following code to reproduce:

```ts
let target: Artboard = sketch.getSelectedDocument().pages[0].layers[0] as Artboard;
let layerObject: any;
let layerObjects = target.sketchObject.children().objectEnumerator();
while (layerObject = layerObjects.nextObject()) {
    // fromNative Layers do not have the property 'type'
    let child = sketch.Layer.fromNative(layerObject);
    console.log(child.type) //undefined
}
```