anchor.diff:  
         nodename = mkOption {
           default = null;
  +        type = types.nullOr types.str;
           description =''
             GVPE node name
           '';
         };
         configText = mkOption {
           default = null;
  +        type = types.nullOr types.lines;
           example = ''
             tcp-port = 655
             udp-port = 655
  
positive.code:       };
        ipAddress = mkOption {
          default = null;
          description = ''
            IP address to assign to GVPE interface
          '';
        };
        subnet = mkOption {
          default = null;
          example = "10.0.0.0/8";
          description = ''
            IP subnet assigned to GVPE network
  
negative.code:       };
        customIFSetup = mkOption {
          default = "";
          type = types.lines;
          description = ''
            Additional commands to apply in ifup script
          '';
  