code: function (fn, create, update) {
    var subscriber = new Subscription(fn, update, this);
  
    // Immediately alias the starting value.
    subscriber.value = subscriber.execute();
    Utils.isFunction(create) && (subscriber.value = create(subscriber.value));
  
    return subscriber;
  }
docs: Subscriber to function in the DOMBars execution instance.
  
  @param  {Function} fn
  @param  {Function} create
  @param  {Function} update
  @return {Object}