def METHOD_NAME(vs, row):
    'Append `row` to vs.source, creating file with correct headers if necessary. For internal use only.'
    if not vs.source.exists():
        with contextlib.suppress(FileExistsError):
            parentdir = vs.source.parent
            if parentdir:
                os.makedirs(parentdir)
        # Write tsv header for Sheet `vs` to Path `p`
        trdict = vs.safe_trdict()
        unitsep = options.delimiter
        with vs.source.open(mode='w', encoding=vs.options.encoding) as fp:
            colhdr = unitsep.join(col.name.translate(trdict) for col in vs.visibleCols) + vs.options.row_delimiter
            if colhdr.strip():  # is anything but whitespace
                fp.write(colhdr)
    with vs.source.open(mode='a', encoding=vs.options.encoding) as fp:
        fp.write('\t'.join(col.getDisplayValue(row) for col in vs.visibleCols) + '\n')