the arg is called unused-arguments-ignore-dunder but it is stored in unused-arguments-ignore-dunder-methods. This means that if you want to use this in a config you need to do unused-arguments-ignore-dunder-methods = True
Also we should add a section to the README on how to set these arguments in a config.
I dont mind submitting a PR for both. Do you want to make the arg name unused-arguments-ignore-dunder-methods or do you want to change the destination to unused-arguments-ignore-dunder?
Thanks,
Rob