Turn on iPhone torch using ARKit

Hi, I'm doing an AR app for iOS with ARKit and need to be able to turn on the torch for low-light conditions. I can turn on the torch via vuforia using this method but enabling Vuforia overrides the ARKit camera-feed so the screen is all black.
I have found this answer on how to do it in swift but I have no idea where to put that script and how to access it from a unity UI button. Any ideas or suggestions of where to look?