def METHOD_NAME(headers: Headers, key: str) -> None:
    """
    Build a handshake response to send to the client.
    Update response headers passed in argument.
    Args:
        headers: Handshake response headers.
        key: Returned by :func:`check_request`.
    """
    headers["Upgrade"] = "websocket"
    headers["Connection"] = "Upgrade"
    headers["Sec-WebSocket-Accept"] = accept(key)