Why should I use the source code of nametuple replace(‘,‘, ‘ ‘). Split() instead of split(‘,‘)

Recently in to see Python Of collections Bag nametuple Source code , See two lines of string manipulation ：

if isinstance(field_names, str):
    field_names = field_names.replace(',', ' ').split()

I'm curious , If you want to separate strings with commas , direct writing ：

field_names = field_names.split(',')

Just fine .

Later, I realized that it was to be compatible with the situation of space segmentation . The source code can be written either by comma or by space , And it can be mixed ; But my writing only supports comma division .