def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def _reset_exiter(cls, exiter: Optional[Exiter]) -> None:
        """Class state:

        - Overwrites `cls._exiter`.
        Python state:
        - Overwrites sys.excepthook.
        """
        logger.debug(f"overriding the global exiter with {exiter} (from {cls._exiter})")
        # NB: mutate the class variables! This is done before mutating the exception hook, because the
        # uncaught exception handler uses cls._exiter to exit.
        cls._exiter = exiter
        # NB: mutate process-global state!
        sys.excepthook = cls._log_unhandled_exception_and_exit