Correctly escape strings for current Python versions

[dbrnz]

To resolve:

/Users/dbro078/Flatmaps/mapmaker-main/.venv/lib/python3.12/site-packages/pyontutils/identity_bnode.py:280: SyntaxWarning: invalid escape sequence '\u'
  sortlast = b'\uf8ff'

[NobleCoder69]

Hi! I'd like to take this issue. Could you please assign it to me?