public function extractDefaultDataFromDataStructure($dataStructure)
    {
        $returnXML = '';
        $sheetArray = [];
        if ($dataStructure) {
            $structureArray = GeneralUtility::xml2array($dataStructure);
            if (!isset($structureArray['sheets']) && isset($structureArray['ROOT'])) {
                $structureArray['sheets']['sDEF']['ROOT'] = $structureArray['ROOT'];
                unset($structureArray['ROOT']);
            }
            if (isset($structureArray['sheets']) && !empty($structureArray['sheets'])) {
                foreach ($structureArray['sheets'] as $sheetName => $sheet) {
                    if (is_array($sheet['ROOT']['el']) && !empty($sheet['ROOT']['el'])) {
                        $elArray = [];
                        foreach ($sheet['ROOT']['el'] as $elName => $elConf) {
                            $config = $elConf['TCEforms']['config'];
                            $elArray[$elName]['vDEF'] = $config['default'];
                            if (!$elArray[$elName]['vDEF'] && $config['type'] === 'select' && !empty($config['items'])) {
                                $elArray[$elName]['vDEF'] = $config['items'][0][1];
                            }
                        }
                        $sheetArray['data'][$sheetName]['lDEF'] = $elArray;
                    }
                }
            }
            if (!empty($sheetArray)) {
                $flexformTools = GeneralUtility::makeInstance(FlexFormTools::class);
                $returnXML = $flexformTools->flexArray2Xml($sheetArray, true);
            }
        }

        return $returnXML;
    }