def find_write_contribs() -> None:
    """Look for files, find authors, sort, write file."""
    map_file_auth = {}  # type: Dict[str, List[str]]
    for filename in scantree('cltk'):
        filepath = filename.path  # type: str
        authors_list = get_authors(filepath)  # type: List[str]
        if authors_list:
            map_file_auth[filepath] = authors_list

    map_auth_file = defaultdict(list)  # type: Dict[str, List[str]]
    for file, authors_file in map_file_auth.items():
        for author in authors_file:
            map_auth_file[author].append(file)
    # now sort the str contents of the list value
    map_auth_file = sort_def_dict(map_auth_file)
    map_auth_file_sorted = sorted(map_auth_file.items())  # type: List[Tuple[str, List[str]]]
    map_auth_file = OrderedDict(map_auth_file_sorted)

    write_contribs(map_auth_file)
Look for files, find authors, sort, write file.