I'm really glad you found it useful! As for your questions; yeah, the federation file is supposed to list all the accounts that you want to modify; in the case of a custom attribute, I'm afraid you need to modify the python script in order to take that into account. It's pretty simple in fact: add another field in the federation file with the data you need and change the python script to read from that attribute.
James Waldrop
Thanks for writing up this article and project. I got lost on the federation and custom schema files. Is the federation file supposed to list the accounts you want to modify? What would you do if you have a custom attribute that requires a value. For example AWS AppStream requires an attribute AWSAttribute with a multi-value field AppStreamCAD .