The multiprocessing.manager.BaseManager class has a class property called _Server, defaulting to multiprocessing.manager.Server, that is used in the ._run_server method (typically invoked via .run()) to determine the class of the server that is to be created.

On the other hand, the .get_server() method creates an instance of Server independent of what is configured in ._Server. Thus, managers started via .run() behave slightly different than those started with .get_server().serve_forever(), and in a way that is hard to track.

I am aware that the ._Server property is undocumented, but it's quite useful when extending BaseManager in a way that it needs to be configured by the server.

I suggest to have .get_server() use ._Server instead of Server; I can't think of situations in which this does the wrong thing (rather, I assume that up to now, users of ._Server didn't try running with .get_server().serve_forever(); it seems ._Server is not used in the standard library).