How to use forEach in Ember inside firebase push()

I had a function that was saving multiple todos to a list.

        list.save().then(function(list) {
              list.get('todos').then(function(todos){
                todos.forEach(function(todo){
                    todo.save();
                });
              });
            });

user.get('todos').then(function(user){
user.save();
)};

But now I'm using Firebase to store session.uid, so I need to use instead

    ref.child('lists').push({
        user: uid,
todo: this.get('todo')

    });

But it doesn't work. (Also I don't know where forEach from the previous version of code fits in here). I've tried

todo: this.get('model.todo')

as well. I think it's because of the way todos are added (I'm saving todos only after list is saved because of parent-child relationship)

addTodo: function() {
    var user = this.controllerFor('application').get('model');

    var todo = this.store.createRecord('todo', {
        title: this.get('model.todos.title'),
        user: user,
    });

    var list = this.get('model');

    list.get('todos').pushObject(todo);  

I'm getting the error

Firebase.push failed: first argument contains undefined in property 'lists.todo'

Any help would be appreciated!