Need some help with my custom import tool

I built a tool to pull data from an API and importing that data into new products. It’s a tool to import Magic: the Gathering cards as porducts. However, I am rather stuck at Attributes. I have the custom product attributes created, but I can’t seem to get a value attached to a product attribute in my tool. Here is the code if anybody can assist.

https://github.com/SeleneSoftware/MagicCardImporter