Use another instance, provided as argument.

def do_use(self, args):
        """Use another instance, provided as argument."""
        self.instance = args
        self.prompt = self.instance + '> '

        archive = self._client.get_archive(self.instance)
        self.streams = [s.name for s in archive.list_streams()]
        self.tables = [t.name for t in archive.list_tables()]