code: public function getTemporaryFilename($extension = 'xlsx')
      {
          $temporaryFilename = tempnam($this->getTemporaryFolder(), 'phpspreadsheet-');
          unlink($temporaryFilename);
  
          return $temporaryFilename . '.' . $extension;
      }
docs: Return a random temporary file name.
  
  @param string $extension
  
  @return string