data io - change from_cmdstanpy to work with CmdStanPy version 0.9.…

…68 (#1558)

* from_cmdstanpy for v0.9.68

* from_cmdstanpy for v0.9.68

* lint fix

* lint fix

* echanges per code review, also, refactor

* lint fix

* added docstrings

* docstrings lint fix

* docstrings lint fix

* lintfix, baby one more time