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 image_url(self, name, override_receipt_id=None):
        """
        We dynamically generate this, since we want it the expiration clock to
        start when the message is created, not when the record is created.

        Arguments:
            name (str): Name of the image (e.g. "photo_id" or "face")

        Keyword Arguments:
            override_receipt_id (str): If provided, use this receipt ID instead
                of the ID for this attempt.  This is useful for reverification
                where we need to construct a URL to a previously-submitted
                photo ID image.

        Returns:
            string: The expiring URL for the image.

        """
        path = self._get_path(name, override_receipt_id=override_receipt_id)
        return self._storage.url(path)