def parse_file_arg(arg):
    """Handles @file format for users, to load the list of users from said file, one per line."""
    if not isinstance(arg, list):
        arg = [arg]
    ret = []
    for val in arg:
        if val[0] == '@':
            with open(val[1:]) as arg_file:
                ret.extend(arg_file.readlines())
        else:
            ret.append(val)
    return [x.strip() for x in ret if x.strip() != '']