How to create .drawing file for PencilKit?

If you look at Apple's

PencilKit

Sample, you'll noticed apple used a dataset file called

Notes.dataset

to save

Pencilkit

draws. Inside the

Notes.dataset

, it contains a general json file for Asset Catalogue.

But more interesting, there is a file called

color.drawing

, which saves the actual data produced by

Pencilkit

. My question is, how do you create this file as a developer? For example, I want to create a tutorial using

Pencilkit

and save it as a ".drawing" file, to load up on first launch.