def header_row(add_rv=False) -> str:
    """Header row for output file."""
    if add_rv:
        header = (
            "temp,logg,feh,alpha,band,resolution,vsini,sampling,"
            "rv,correctflag,quality,cond1,cond2,cond3\n"
        )
    else:
        header = (
            "temp,logg,feh,alpha,band,resolution,vsini,sampling,"
            "correctflag,quality,cond1,cond2,cond3\n"
        )
    return header