def check_ext(f_name, ext):
    """Check the extension for a file name, and add if missing.

    Parameters
    ----------
    f_name : str
        The name of the file.
    ext : str
        The extension to check and add.

    Returns
    -------
    str
        File name with the extenion added.
    """
    return f_name + ext if not f_name.endswith(ext) else f_name
