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 Exists(self):
    """Returns True if the log group exists."""
    describe_cmd = util.AWS_PREFIX + [
        '--region', self.region,
        'logs', 'describe-log-groups',
        '--log-group-name-prefix', self.name,
        '--no-paginate'
    ]
    stdout, _, _ = vm_util.IssueCommand(describe_cmd)
    log_groups = json.loads(stdout)['logGroups']
    group = next((group for group in log_groups
                  if group['logGroupName'] == self.name), None)
    return bool(group)