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 _get_path(self, prefix, override_receipt_id=None):
        """
        Returns the path to a resource with this instance's `receipt_id`.

        If `override_receipt_id` is given, the path to that resource will be
        retrieved instead. This allows us to retrieve images submitted in
        previous attempts (used for reverification, where we send a new face
        photo with the same photo ID from a previous attempt).
        """
        receipt_id = self.receipt_id if override_receipt_id is None else override_receipt_id
        return os.path.join(prefix, receipt_id)