        def _log_cls(name, cls):
            """Log a configured class

            Logs the class and version (if found) of Authenticator
            and Spawner
            """
            # try to guess the version from the top-level module
            # this will work often enough to be useful.
            # no need to be perfect.
            if cls.__module__:
                mod = sys.modules.get(cls.__module__.split('.')[0])
                version = getattr(mod, '__version__', '')
                if version:
                    version = f'-{version}'
            else:
                version = ''
            self.log.info(
                "Using %s: %s.%s%s", name, cls.__module__ or '', cls.__name__, version
            )
Log a configured class

Logs the class and version (if found) of Authenticator
and Spawner
jupyterhub/app.py