public function cleanAccessTokens(array $param = [])
    {
        $count = 0;

        foreach ($this->getAllStoredAccessTokenFiles() as $file) {
            $expires_at = $this->loadTimestamp($file);

            if (is_integer($expires_at)) {
                if ($expires_at < time()) {
                    unlink($file);
                    $count++;
                }
            }
        }

        return $count;
    }