mitch-at-orika

Posting this incase it helps... I came across an issue like this one on [discourse](https://discourse.pymc.io/t/equvilant-apis-in-pymc-v4/8920) while trying to use v3 code in v4. Trying to do some of the plots...

Thanks for the explanation Michael, it is reassuring it was a BART only option, I originally thought I had just missed this functionality of pymc vars until now.

I dont do this PR on public repos often... I hope I got it all right but there is a PR up there now. Results of the option with no...