pub fn send_extension_event<'c, 'input, Conn>(
    conn: &'c Conn,
    destination: Window,
    device_id: u8,
    propagate: bool,
    events: &'input [EventForSend],
    classes: &'input [EventClass]
) -> Result<VoidCookie<'c, Conn>, ConnectionError>
where Conn: RequestConnection + ?Sized,