protected function loadSubtable($dataTable, $row)
    {
        if (!($this->apiModule && $this->apiMethod && count($this->request))) {
            return null;
        }

        $request = $this->request;

        $idSubTable = $row->getIdSubDataTable();
        if ($idSubTable === null) {
            return null;
        }

        $request['idSubtable'] = $idSubTable;
        if ($dataTable) {
            $period = $dataTable->getMetadata(DataTableFactory::TABLE_METADATA_PERIOD_INDEX);
            if ($period instanceof Range) {
                $request['date'] = $period->getDateStart() . ',' . $period->getDateEnd();
            } else {
                $request['date'] = $period->getDateStart()->toString();
            }
        }

        $method = $this->getApiMethodForSubtable($request);
        return $this->callApiAndReturnDataTable($this->apiModule, $method, $request);
    }