If you want to get configuration settings from some other sources than the built-in sources, you should create a class that derives from :py~layeredconfig.ConfigSource and implement a few methods.
If your chosen source can expose the settings as a (possibly nested) :pydict, it might be easier to derive from :py~layeredconfig.DictSource which already provide implementations of many methods.
layeredconfig.ConfigSource
layeredconfig.DictSource