Looks brilliant!

My only suggestion is here:

> It also ignores any leading, trailing, or duplicate delimiters:

    from textcase import case, convert

    print(convert("IOStream", case.SNAKE))             # io_stream
    print(convert("myJSONParser", case.SNAKE))         # my_json_parser
    print(convert("__weird--var _name-", case.SNAKE))  # weird_var_name

i.e.

    print(convert("__weird--var _name-", case.SNAKE, preserve=True))  # __weird__var__name

Thank you for your suggestion! Adding a preserve option to maintain leading, trailing, and duplicate delimiters while normalizing them to the target delimiter is a great idea. I’ll consider implementing this feature. Thanks again!