def _get_member_types(tag):
    """Return the types of the members, handle wildcards."""
    at1 = tag.attrib.get("type1")
    at2 = tag.attrib.get("type2")
    at3 = tag.attrib.get("type3")
    at4 = tag.attrib.get("type4")

    member_types = filter(lambda x: x is not None, [at1, at2, at3, at4])
    member_types = [
        "*" if mem_type == "" else mem_type for mem_type in member_types
    ]
    return member_types or None