def METHOD_NAME(opt):
    """
    Parse option passed to --test-files into a key-value pair.
    >>> parse_test_files_option('generators.py:10,13,19')
    ('generators.py', [10, 13, 19])
    """
    opt = str(opt)
    if ':' in opt:
        (f_name, rest) = opt.split(':', 1)
        return f_name, list(map(int, rest.split(',')))
    else:
        return opt, []