TypeError: Object #<ServerResponse> has no method 'error'

I am following book 'Node.js In Action' one earlier access version from http://www.manning.com/cantelon/ and the author uses method 'error()' on 'res' object in section about Express. So, the following code that copied from book:

exports.required = function(field){
    field = parseField(field);
    return function(req, res, next){
        if (getField(req,field)){
            next()
        } else {
            res.error(field.join(' ') + ' is required');
...

However, this breaks with the error:

TypeError: Object #<ServerResponse> has no method 'error'

From Node.js docs, i see there is no method for response object. I wonder if there is a middlware that decorates 'res' object with the missing method error() that i need to include. Here is the current configurations:

app.configure(function(){
  app.set('port', process.env.PORT || 3001);
  app.set('views', __dirname + '/views');
  app.set('view engine', 'jade');
  app.set('photos', __dirname + '/public/photos');
  app.use(express.favicon());
  app.use(express.logger('dev'));
  app.use(express.static(path.join(__dirname, 'public')));
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(express.cookieParser('your secret here'));
  app.use(express.cookieSession());
  app.use(user);
  app.use(app.router);
  app.use(express.errorHandler());
});

If there is none, but you know how to decorate the response object with method error(), I would appreciate if you could share the code snippet for it. thank you