gistfile1.js

var Class1 = function() {
    Class1.superclass.constructor.call(this, config);
}

Class1.NAME = "class1";
Class1.ATTRS = {
    //Several Attributes here
}

Y.extend(Class1, Y.Base, {
    // Several prototype methods here
}

// I want to inherit from Class1 and also get its Attributes
var Class2 = function(config) {
    Class2.superclass.constructor.apply(this,arguments);
    var attrs = {
        width: {},
        height: {}
    };
    this.addAttrs(attrs, config);
}

Y.mix(Class2, {
    NAME: "class2",
    ATTRS: Class1.ATTRS
});

Y.extend(Class2, Class1, {
    // Class 2 prototype methods here...
});

Changing Class2 to...

var Class2 = function(config) {
Class2.superclass.constructor.apply(this, arguments);
};

Y.mix(Class2, {
NAME: "class2",
ATTRS: {
width: {...},
height: {...}
}
});

Y.extend(Class2, Class2, {
});