def get(self, key: str, default=None) -> Any:
        """Get the value for an arbitrary string config key.
        note: try to use explicit predefined ConfigVars instead of this method, whenever possible.
              This method side-steps ConfigVars completely, and is mainly kept for situations
              where the config key is dynamically constructed.
        """
        assert isinstance(key, str), key
        with self.lock:
            out = self.cmdline_options.get(key)
            if out is None:
                d = self.user_config
                path = key.split('.')
                for key in path[0:-1]:
                    d = d.get(key, {})
                if not isinstance(d, dict):
                    d = {}
                out = d.get(path[-1], default)
        return out
Get the value for an arbitrary string config key.
        note: try to use explicit predefined ConfigVars instead of this method, whenever possible.
              This method side-steps ConfigVars completely, and is mainly kept for situations
              where the config key is dynamically constructed.
        
electrum/simple_config.py