private function getBrowsersCountFromSessions(Carbon $start, Carbon $end)
    {
        return $this->getVisitorsFilteredByDateRange($start, $end)
            ->filter(function (Visitor $visitor) {
                return $visitor->hasUserAgent();
            })
            ->transform(function (Visitor $visitor) {
                return $visitor->agent;
            })
            ->groupBy('browser')
            ->transform(function (Collection $items, $key) {
                return [
                    'name'  => $key,
                    'count' => $items->count(),
                ];
            })
            ->sortByDesc('count');
    }