def citation_authority(file_identifier: str):
    """
    Helper function to extract citation authority (kind of originator center reverse DNS) from file identifier

    :param file_identifier: Identifier of the file (metadata document) to extract the authority from.

    :returns: citation authority, or empty string if the extraction failed
    """

    if file_identifier is not None:
        components = file_identifier.split(':')
        if len(components) > 3:
            return components[3]
    return ''