public function getHeaders(CredentialsInterface $credentials, $method, $url, array $bodyParameters = array())
    {
        $header = $this->protocolHeader(strtoupper($method), $url, $credentials, $bodyParameters);
        $authorizationHeader = array('Authorization' => $header);
        $headers = $this->buildHttpClientHeaders($authorizationHeader);

        return $headers;
    }