public function guessLexer($filename)
    {
        $cmd = sprintf('%s -N %s', $this->binaryPath, $filename);
        $p = new Process($cmd);
        $p->run();
        $output = trim($p->getOutput());
        if ('text' === $output) {
            $output = $this->guessFromExtension($filename);
        }
        if ('text' === $output) {
            $output = $this->guessFromContent($filename);
        }

        return $output;
    }