private function parseOptions(array $options)
    {
        if (isset($options['headers']) && is_array($options['headers'])) {
            $this->headers = $options['headers'];
        }

        if (isset($options['scheme']) && strtolower($options['scheme']) === 'http') {
            $this->scheme = 'http';
        }

        if (isset($options['output_format']) && strtolower($options['output_format']) === 'xml') {
            $this->outputFormat = 'xml';
        }
    }