protected function getDevicesFromSessions(Carbon $start, Carbon $end)
    {
        return $this->getVisitorsFilteredByDateRange($start, $end)
            ->filter(function (Visitor $session) {
                return $session->hasDevice();
            })
            ->transform(function (Visitor $session) {
                return $session->device;
            })
            ->groupBy('kind')
            ->transform(function (Collection $items, $key) {
                return [
                    'kind'  => trans("tracker::devices.kinds.$key"),
                    'count' => $items->count(),
                ];
            });
    }