Coverting JSON to mask with shape_type='mask'

[AmaiaGaste]

I tried to use the labelme.utils.shape_to_mask function and I get the following error: AssertionError: Polygon must have points more than 2.

It seems there is an assert that checks if there is more than 2 points and my JSON only as 2 points and a mask. I want to convert the JSON into a PNG or JPG mask so that I can use the annotated image as ground truth. Thank you!