def get_clc(goods):
    """Return a list of the unique control list entries for all goods in the supplied list.

    A single good may be passed instead of a list of one item.
    """
    if not isinstance(goods, list):
        goods = [goods]

    clcs = {clc["rating"] for good in goods for clc in good.get("good", {}).get("control_list_entries", []) if clc}
    return sorted(clcs - {None})