toJSON and mlClass attribute properties

gistfile1.js

// use as follows (can be combined)

{   
    ATTRS: {
        total: { value: 0, toJSON: false },
        lines: { value: null, setter: '_setML', mlClass: Y.App.Manage.ML.Lines }
    }   
}   

// base class definition

YUI.add(
    "custom-manage-m-base",
    function (Y) {
        Y.Base._ATTR_CFG.concat("toJSON");
        Y.Base._ATTR_CFG_HASH.toJSON = true;
        Y.Base._ATTR_CFG.concat("mlClass");
        Y.Base._ATTR_CFG_HASH.mlClass = true;
        
        var Clazz = Y.namespace("App.Manage.M").Base = Y.Base.create(
            "custom_manage_m_base",
            Y.Model,
            [], 
            {   
                _setML: function (list, name) {
                    Y.log(Clazz.NAME + "::_setML: " + name);
                    
                    var existing_list = this.get(name);
                    if (existing_list) {
                        return existing_list.reset(list);
                    }
                    
                    var ml_class = this._getAttrCfg(name).mlClass;
                    
                    Y.log(Clazz.NAME + "::_setML - creating new list");
                    var new_list = new ml_class (
                        {   
                            bubbleTargets: this
                        }
                    );
                    new_list.reset(list);
                    
                    return new_list;
                },
                
                toJSON: function () {
                    Y.log(Clazz.NAME + "::toJSON");
                    
                    var attrs = Clazz.superclass.toJSON.apply(this, arguments);
                    Y.each(
                        attrs,
                        function (v, k, o) {
                            var attr_cfg = this._getAttrCfg(k);
                            
                            if (Y.Lang.isValue(attr_cfg.toJSON) && ! attr_cfg.toJSON) {
                                delete attrs[k];
                            }   
                        },  
                        this
                    );  
                    
                    return attrs;
                }   
            },  
            {
                ATTRS: {}   
            }   
        );  
    },  
    "0.0.1",
    {
        requires: [
            "model"
        ]   
    }
);