public function addHeaders(
        $headers,
        $personalizationIndex = null,
        $personalization = null
    ) {
        if (current($headers) instanceof Header) {
            foreach ($headers as $header) {
                $this->addHeader($header);
            }
        } else {
            foreach ($headers as $key => $value) {
                $this->addHeader(
                    $key,
                    $value,
                    $personalizationIndex,
                    $personalization
                );
            }
        }
    }