def create_software_id(regid, unique_id):
    """
    Create a Software-ID by joining the Regid and the Unique-ID with a double underscore.

    Args:
        regid (str):
            The Regid string.
        unique_id (str):
            The Unique-ID string.

    Returns:
        The Software-ID string.

    """
    return '{regid}__{unique_id}'.format(regid=regid, unique_id=unique_id)
