如何在PHPSpreadSheet PHP中检查工作表是否完全为空

I am currently getting the active sheet like this:

  $oReader = new \PhpOffice\PhpSpreadsheet\Reader\Xlsx();
  $spreadSheet = $oReader->load("spread_sheet.xlsx");
  $oSheet = $spreadSheet->getActiveSheet();

But before to check its data, I need to know if not is empty.

Is there a way to check if a sheet is fully empty with PhpSpreadSheet ?