public function getSubuserMonthly(
        $subuser = null,
        $sortByMetric = 'delivered',
        $sortByDirection = 'desc',
        $limit = 5,
        $offset = 0
    ) {
        $this->validateOptions(
            'sortByDirection',
            $sortByDirection,
            self::OPTIONS_SORT_DIRECTION
        );
        $this->validateInteger('limit', $limit);
        $this->validateInteger('offset', $offset);
        return [
            'date' => $this->startDate,
            'subuser' => $subuser,
            'sort_by_metric' => $sortByMetric,
            'sort_by_direction' => $sortByDirection,
            'limit' => $limit,
            'offset' => $offset
        ];
    }