func extractRespElements(w http.ResponseWriter) map[string]string {
	if w == nil {
		return map[string]string{}
	}
	return map[string]string{
		"requestId":      w.Header().Get(xhttp.AmzRequestID),
		"nodeId":         w.Header().Get(xhttp.AmzRequestHostID),
		"content-length": w.Header().Get(xhttp.ContentLength),
		// Add more fields here.
	}
}

// Trims away `aws-chunked` from the content-encoding header if present.