protected function getCssAsset(string $filename, string $newExtension): string
    {
        $extensionlessFilename = pathinfo($filename, PATHINFO_FILENAME);
        /** @var int $filenamePosition */
        $filenamePosition = strrpos($filename, $extensionlessFilename);
        $relativePath = substr($filename, 0, $filenamePosition);
        return "$relativePath$extensionlessFilename.$newExtension";
    }