How to filter an Association?

I want to be able to filter a association, as in the example below only bring the emails assets of a particular user.

``` javascript
var User =  db.define('user', ...);
var Email = db.define('email', ...);
Email.hasOne('user', User, {required: true, reverse: 'emails'});


user.getEmails().find({active: true}).run(...);
user.getEmails().where("active = ?", [true]).all(...);
```
