anchor.diff:  
     ###### implementation
   
  -  config = mkIf config.services.gvfs.enable {
  +  config = mkIf cfg.enable {
   
  -    environment.systemPackages = [ pkgs.gnome3.gvfs ];
  +    environment.systemPackages = [ cfg.package ];
   
  -    services.dbus.packages = [ pkgs.gnome3.gvfs ];
  +    services.dbus.packages = [ cfg.package ];
   
  -    systemd.packages = [ pkgs.gnome3.gvfs ];
  +    systemd.packages = [ cfg.package ];
   
       services.udev.packages = [ pkgs.libmtp.bin ];
   
  
positive.code: 
        enable = mkEnableOption "GVfs, a userspace virtual filesystem";
  
      };
  
    };
  
negative.code: { config, lib, pkgs, ... }:
  
  with lib;
  
  let
  
    cfg = config.services.gvfs;
  
  in
  
  {
  
  