Sub documents inheritance in mongoose and mongoose-schema-extend

Question

I have tried to implement inheritance for mongoDB sub document using mongoose-schema-extend, and later with mongoose itself. The basic requirement is to define additional properties in inheriting class and get them on DB- this works fine in both approaches. The second requirement is to be able to distinguish between types- using discriminatorType and instanceOf. discriminatorType was not saved in DB using mongoose-schema-extend, only using mongoose discriminator directly. instanceOf did not work at both cases (after parentDocument.find)- the pockets seems to be Object only.

Code for mongoose-schema-extend:

var PocketSchema = new mongoose.Schema({
    name: {type: String, unique: true , required: true}, //required - not working within array
    status: {type: String , enum :['ACTIVE','RETIRED'], Default:'ACTIVE' },
    limits : ['Limit']
},{ discriminatorKey : '_type' });

dbConn.model('Pocket', PocketSchema);

var CreditCardPocketSchema =dbConn.models.Pocket.schema.extend({
  PAN :  {type: String, required: true } 
});

dbConn.model('CreditCardPocket', CreditCardPocketSchema);

var customerSchema = mongoose.Schema({
    username: {type: String, unique: true, required: true } ,
    password: String,
    email: { type: String },
    status: {type: String , enum :['REGISTERED','ACTIVE','RETIRED'] , Default:'REGISTERED'},
    pockets : ['Pocket']
});

Code for mongoose with util.extend:

function PocketSchema() {          
mongoose.Schema.apply(this, arguments);         
this.add({                             
    name: {type: String, unique: true , required: true},//required - not working within array
    status: {type: String , enum :['ACTIVE','RETIRED'], Default:'ACTIVE' },
    limits : ['Limit']
});                                    
};      
util.inherits(PocketSchema, mongoose.Schema);
var pocketSchema = new PocketSchema();

dbConn.model('Pocket', pocketSchema);

var CreditCardPocketSchema = new PocketSchema({
    PAN :  {type: String, required: true } 
});

dbConn.models.Pocket.discriminator('CreditCardPocket', CreditCardPocketSchema);

**Code for checking instanceOf: **

exports.showPockets = function(req, res){
var username = req.params.username;

dbConn.models.Customer.findOne({username:username},function(err,user) {
    if (user === null) {
        res.send('user does not exist');
    }else {
        user.pockets[0] instanceof dbConn.models.CreditCardPocket;
        user.pockets[0] instanceof dbConn.models.Pocket;

        dbConn.models.Pocket.prototype.isPrototypeOf(user.pockets[0]);
        dbConn.models.SVAPocket.prototype.isPrototypeOf(user.pockets[0]);
    }
});
};

Is mongoose-schema-extend discriminator not working properly for sub documents? and for instanceOf -shouldn't this return true?

Thanks in advance.