code: private function readMsoDrawingGroup()
      {
          $length = self::getUInt2d($this->data, $this->pos + 2);
  
          // get spliced record data
          $splicedRecordData = $this->getSplicedRecordData();
          $recordData = $splicedRecordData['recordData'];
  
          $this->drawingGroupData .= $recordData;
      }
docs: Read MSODRAWINGGROUP record.