protected function normalizeHeaders(array $headers)
    {
        if (empty($headers["User-Agent"]))
            $headers["User-Agent"] = "evias NEM Blockchain Wrapper";

        if (empty($headers["Accept"]))
            $headers["Accept"] = "application/json";

        if (empty($headers["Content-Type"]))
            $headers["Content-Type"] = "application/json";

        return $headers;
    }