public static function sanitizeComboSetSelections($grouptoitemmap) {
        // sort for serialization
        ksort($grouptoitemmap);
        foreach ($grouptoitemmap as $groupid => $itemids) {
            $itemids = !empty($itemids) ? (array)$itemids : [];
            // sort for serialization
            sort($itemids);
            $cleanselections = [];
            // strip all -1 values since they represent no selection. All values outside of -1 are
            // processed as explicit selections
            foreach ($itemids as $selitemid) {
                if ((int)$selitemid !== -1) {
                    $cleanselections[] = (int)$selitemid;
                }
            }
            // sanitize request map for easier processing
            $grouptoitemmap[$groupid] = $cleanselections;
        }

        return $grouptoitemmap;
    }