Gojs testing from QA perspective automation using python selenium framework

Hello Team,
We have an application developed using Gojs Canvas and there are interactive diagrams I need to test if correct or not as per the design rules approved. I’m using python selenium framework to automate other web application UI functionality and want to extend this framework to test Gojs diagrams as well.
As selenium needs access to DOM to use locators of the elements and Canvas just does not use DOM elements, I am seeking some help how I can perform the testing on canvas.
The extensions Robot and Jest suggested at Testing GoJS apps -- Northwoods Software
can be used for unit testing but I can not use it for QA test automation using Python and Selenium.
Also I went through existing threads about this but not helping to resolve my issue to access diagrams.
Any pointers or suggestion will be helpfull.