how to save a object in ember data when model consists of more then one object?

in ember 2.7 with ember data i have a route with models created with 'RSVP.hash' like the example here :

model: function(params){
    return Ember.RSVP.hash({
        customer: this.store.findRecord('customer', params.customer_id),
        address: this.store.createRecord('address')
    });

I want to save the 'address' part of the model ? model.save() gives as result: 'Uncaught TypeError: model is not a function' what can i do to save only the address part of the model ?