setAttribute

Hi,

How can one add attribute (new field)
to existing element

for example (which is also might be a bug -when downloading stanza.io)
the plugin declare

var Affiliation = JXT.define({
name: 'affiliation',
namespace: _xmppConstants.Namespace.PUBSUB_OWNER,
element: 'affiliation',
fields: {
node: Utils.attribute('node'),
type: Utils.attribute('affiliation'),

    }
});

I want to extend it to be

var Affiliation = JXT.define({
name: 'affiliation',
namespace: _xmppConstants.Namespace.PUBSUB_OWNER,
element: 'affiliation',
fields: {
node: Utils.attribute('node'),
type: Utils.attribute('affiliation'),
//added field
jid: Utils.jidAttribute('jid')
}
});

something like:

jxt.withDefinition('affiliation', NS, function (affiliation) {
//what do I do here?
});

thanks,
Lior