Trouble with allowUnfreePredicate

I am trying to install Steam. I have read the Unfree Software wiki page and followed the Steam nixos wiki about how to install it, but it gives the error undefined variable 'lib'. I have seen other similar posts but all of them seem to be about troubles with flakes (which I don’t use). ▶ Full terminal output ▶ configuration.nix I have tried changing lib for nigpkgs but that gives another error. Idk if it’s something super obvious that I’m missing but I would really appreciate the help.