Extra parameters for startLogging (Twisted)?

In Twisted docs, startLogging API supports *a and **kw e开发者_如何学Pythonxtra arguments. What can I use these for?

There's just one more parameter you can pass, setStdout. See the documentation for startLoggingWithObserver for details about what it does.

I'm not sure they are used at all. See Samples and documentation where they are not used nor mentioned. Also, after reviewing the source code, it doesn't seem to use them.