fetching relations in Alloy model

question.js

  extendModel: function(Model) {    
    _.extend(Model.prototype, {
      answers: function() {
        var coll = Alloy.createCollection('answer');
        coll.fetch({ query: 'select * from answers where question_id = ' + this.get('id')});
        return coll;
      },
    });
    return Model;
  }