Extracting the updated prior parameter values

Have you been able to run https://docs.pymc.io/projects/examples/en/latest/pymc3_howto/updating_priors.html as is locally on your computer? Do you understand what is happening in each of the steps?

I don’t think this is possible with pymc.MultiTrace but you can do that after converting to inferencedata using trace.posterior.rename(). After renaming however, you won’t be able to pass this trace to sample_posterior_predictive anymore.