code: protected function writeAsset(string $asset_contents)
      {
          // Tell the world what we are doing
          $this->printTaskInfo('Writing to final asset - <info>'.$this->destination->getPathname().'</info>');
  
          // Write the normal asset
          if (file_put_contents($this->destination->getPathname(), $asset_contents) === false)
          {
              throw new RuntimeException
              (
                  'Failed to write asset: '.$this->destination->getPathname()
              );
          }
  
          // Create a gzipped version of the asset
          if ($this->debug === false && $this->gz === true)
          {
              $gz_file_name = $this->destination->getPathname().'.gz';
  
              $gz_contents = gzencode($asset_contents);
  
              // Tell the world what we are doing
              $this->printTaskInfo('Writing gzipped version of final asset - <info>'.$gz_file_name.'</info>');
  
              if (file_put_contents($gz_file_name, $gz_contents) === false)
              {
                  throw new RuntimeException
                  (
                      'Failed to write gzipped version of asset: '.
                      $gz_file_name
                  );
              }
          }
      }
docs: The business end, finally lets actually save the
  compiled / minified asset.
  
  @param string $asset_contents