anchor.diff: -{ config, pkgs, ... }:
  +{ config, pkgs, lib, ... }:
   
   let
     unstableTarball = fetchTarball https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz;
  
positive.code:         unstable = unstablePkgs;
          # Make a special opentabletdriver exception since it is needed by module above.
          opentabletdriver = unstablePkgs.opentabletdriver;
        })
      ];
    };
  
negative.code: in {
    # Backport module from unstable.
    imports = [ "${unstableTarball}/nixos/modules/hardware/opentabletdriver.nix" ];
    # disabledModules = [ "hardware/opentabletdriver.nix" ];
  
    nixpkgs = {
      config = {
  