anchor.diff:  
       font = mkOption {
         default = null;
  -      type = types.nullOr types.string;
  +      type = types.nullOr types.str;
         example = "Droid Sans Mono 14";
         description = "Font to use.";
       };
  
positive.code: 
      terminal = mkOption {
        default = null;
        type = types.nullOr types.string;
        description = ''
          Path to the terminal which will be used to run console applications
        '';
  
negative.code:     configPath = mkOption {
        default = "${config.xdg.configHome}/rofi/config";
        defaultText = "$XDG_CONFIG_HOME/rofi/config";
        type = types.str;
        description = "Path where to put generated configuration file.";
      };
  
  