public function push($notification, $notifiable)
    {
        if ( ! is_array($notifiable) && ! $notifiable instanceof Traversable) {
            $notifiable = [$notifiable];
        }

        foreach ($notifiable as $toBeNotified) {
            if ( ! $toBeNotified instanceof Notifiable && !$toBeNotified instanceof NotifiableGroup) {
                throw new NotNotifiableException("The notifiable members must implement the notifiable interface.");
            }
        }

        $notification = is_string($notification) ? ['body' => $notification] : $notification;

        foreach ($notifiable as $toBeNotified) {
            $this->pushNotification($notification, $toBeNotified);
        }
    }