```js exports.handler = async (event) => { if (event.headers != undefined) { const headers = toLowerCaseProperties(event.headers);

    if (headers['sec-websocket-protocol'] != undefined) {
        const subprotocolHeader = headers['sec-websocket-protocol'];
        const subprotocols = subprotocolHeader.split(',');

        if (subprotocols.indexOf('myprotocol') >= 0) {
            const response = {
                statusCode: 200,
                headers: {
                    "Sec-WebSocket-Protocol" : "myprotocol"
                }
            };
            return response;
        }
    }
}

const response = {
    statusCode: 400
};

return response;

};function toLowerCaseProperties(obj) { var wrapper = {}; for (var key in obj) { wrapper[key.toLowerCase()] = obj[key]; } return wrapper; } ```