Can't find the way to transform into json file

I've been working on a project building a mini writing plotter called BrachioGraph (https://www.brachiograph.art/en/latest/how-to/use-linedraw/). In its instructions, he says that you can use this linedraw.py library to transform images in to json files that the arm can read. However, this code can not do that. Does anybody know how to solve this? Thank you