public static function saveSession()
    {
        if (!empty(self::$instance)) {
            foreach (self::$instance as $event) {
                $experiment = Experiments::firstOrCreate([
                    'experiment' => $event->name,
                    'goal' => $event->goal,
                ]);

                $event = Events::firstOrCreate([
                    'instance_id' => self::$session->id,
                    'name' => $event->name,
                    'value' => $event->fired,
                ]);

                $experiment->events()->save($event);
                self::$session->events()->save($event);
            }
        }

        return  Session::get(config('laravel-ab.cache_key'));
    }