gOutputStreamFlush.gOutputStreamFlushAsync(object, io.priority = 0, cancellable = NULL, callback, user.data = NULL)objectio.prioritycancellableGCancellable object, NULL to ignore.callbackGAsyncReadyCallback to call when the request is satisfieduser.datacallback will be
called. You can then call gOutputStreamFlushFinish to get the
result of the operation.