How to define instance methods for models with sails.js

How can I define functions/instance method for objects in Sails ?

In Waterline doc (https://github.com/balderdashy/waterline) they say:

var User = Waterline.Collection.extend({
...
  attributes: {
    ...
    // You can also define instance methods here
    fullName: function() {
      return this.firstName + ' ' + this.lastName
    }
  },
}

But when I try do define an instance method in attributes in a model in Sails, the function is not added to the object. Am I doing something wrong ?

Environment: Sails (v0.8.94), Node (v0.8.16)