// categorized array of results
    public function getCategResultsAttribute(){

        // question categories
        $categories = InsCategory::select('cat_id', 'name')
            ->get();

        $out = [];
        foreach ($categories as $cat) {
            $obj = [
                'cat_name' => $cat->name,
                'results' => []
            ];

            // questionnaires
            $chks = InsChecklist::where('cat_id', $cat->cat_id)
                ->select('chk_id', 'chk_desc')
                ->get();

            foreach($chks as $chk){
                $res = InsResult::where('chk_id', $chk->chk_id)
                    ->select('res_id', 'head_id', 'chk_id', 'ispassed')
                    ->where('head_id', $this->head_id)
                    ->first();

                if ($res){
                    array_push($obj['results'], [
                        'res_id' => $res->res_id,
                        'desc' => $chk->chk_desc,
                        'ispassed' => $res->ispassed
                    ]);
                }
            }
            if (count($obj['results']) > 0)
                array_push($out, $obj);

        }


        return $out;
    }