Update library to support python 3.12 and pandas>=2.0

[ybubnov]

This patch fixes a unescaped string symbols, like "\s", which are raising SyntaxError in Python 3.12 by replacing strings with raw strings.

Also patch changes series iteration iteritems(), which was removed in Pandas>=2.0 and replaces it with iloc iterator, which is available in both, Pandas<2.0 and Pandas>=2.0

Patch also bumps version of the library to 0.3.7.

[ybubnov]

@multimeric I'd appreciate getting a review on this PR.