anchor.diff:  
         drivers = mkOption {
           type = types.listOf types.path;
  +        default = [];
           example = literalExample "[ pkgs.splix ]";
           description = ''
             CUPS drivers to use. Drivers provided by CUPS, cups-filters, Ghostscript
  
positive.code:           [ config.environment.etc."cups/cups-browsed.conf".source
            ];
        };
  
      services.printing.drivers =
        [ cups pkgs.ghostscript pkgs.cups_filters additionalBackends
          pkgs.perl pkgs.coreutils pkgs.gnused pkgs.bc pkgs.gawk pkgs.gnugrep
        ];
  
      services.printing.cupsFilesConf =
        ''
  
negative.code:   # cupsd.conf tells cupsd to use this tree.
    bindir = pkgs.buildEnv {
      name = "cups-progs";
      paths =
        [ cups additionalBackends cups_filters pkgs.ghostscript ]
        ++ cfg.drivers;
      pathsToLink = [ "/lib/cups" "/share/cups" "/bin" "/etc/cups" ];
      postBuild = cfg.bindirCmds;
      ignoreCollisions = true;
  