Invalid escape sequences in docstrings

[ehossack]

When running the library with python 3.12, I see the following:

/usr/local/lib/python3.12/site-packages/b2sdk/file_version.py:219: SyntaxWarning: invalid escape sequence '\_'
"""
/usr/local/lib/python3.12/site-packages/b2sdk/raw_simulator.py:1162: SyntaxWarning: invalid escape sequence '\?'
'/b2api/v[0-9]+/b2_download_file_by_id\?fileId=(?P<file_id>[^/]+)',
usr/local/lib/python3.12/site-packages/b2sdk/v2/file_version.py:27: SyntaxWarning: invalid escape sequence '\_'