Mongoosejs: How to create a model without Schema?

I have found this tutorial: http://dailyjs.com/2010/12/06/node-tutorial-5/

which uses a slightly different approach from build model schemas then the mongoosejs.com docs.

It doesn't creates the MongooseModel with help of mongoose.Schema:

var Some = mongoose.model('Some', new mongoose.Schema({
    property: { Type: String }
}), 'Somes');

but with something like:

var Some = mongoose.model('Some', {
    setters: {
        toLowerCase: function(string) {
            return string.toLowerCase();
        }
    }
}, 'Somes');

I personally have less issues with the second method and can read better in. Unfortunatly there isn't any information about this approach in the docs...

Have there some already experience with this way to define mongoose models? Where do I find more docs about?

Regards