def file_with_extension(file_name, extension):
    """
    Returns file with extension if it's not in file name.
    :param file_name: <str> -> name of the file
    :param extension: <str> -> extension of the file
    :return: <str> -> file name with extension
    """
    if file_name.split('.')[-1] != extension:
        return f'{file_name}.{extension}'
    return file_name