I think you have missed something important here:

    >>> data = b'foo\bar'
    >>> len(data)
    6
    >>> print(data)
    b'foo\x08ar'


If you want bytes including a backslash followed by a b, you need to use raw bytes rb'foo\bar' or escape the backslash.

Also Python 3.8 is in feature-freeze so the earliest this new feature could be added to the language is now 3.11.