protected function getClientOptions()
    {
        $options = $this->getOptions();
        if (!isset($options['headers']) || !isset($options['headers']['Content-Type'])) {
            $options['headers']['Content-Type'] = ['application/json'];
        } else {
            if (!in_array('application/json', $options['headers']['Content-Type'])) {
                $options['headers']['Content-Type'][] = ['application/json'];
            }
        }
        return $options;
    }