Fatal error: Uncaught Error: Class "OpenSpout\Writer\AbstractWriterMultiSheets" not found in /srv/www/htdocs/moodle/lib/openspout/src/Writer/XLSX/Writer.php:21 Stack trace: #0 {main} thrown in /srv/www/htdocs/moodle/lib/openspout/src/Writer/XLSX/Writer.php on line 21