/**
* This function should return a path to an image representation of the given file.
*/
public function convert(string $file, Conversion $conversion = null) : string
{
$pathToImageFile = pathinfo($file, PATHINFO_DIRNAME).'/'.pathinfo($file, PATHINFO_FILENAME).'.jpg';
// Here you should convert the file to an image and return generated conversion path.
\PowerPoint::convertFileToImage($file)->store($imageFile);
return $imageFile;
}