anchor.diff:        label = mkOption {
           default = null;
           example = "root-partition";
  -        type = types.nullOr types.str;
  +        type = types.nullOr nonEmptyStr;
           description = "Label of the device (if any).";
         };
   
  
positive.code:         default = [ "defaults" ];
          example = [ "data=journal" ];
          description = "Options used to mount the file system.";
          type = types.listOf types.str;
        };
  
      };
  
negative.code: 
        mountPoint = mkOption {
          example = "/mnt/usb";
          type = nonEmptyStr;
          description = "Location of the mounted the file system.";
        };
  
        device = mkOption {
          default = null;
          example = "/dev/sda";
          type = types.nullOr nonEmptyStr;
          description = "Location of the device.";
        };
  
        fsType = mkOption {
          default = "auto";
          example = "ext3";
          type = nonEmptyStr;
          description = "Type of the file system.";
        };
  
  