It is also worth noting that to_inference_data is only available for PyMC3 4.x, which has not yet been released and doesn’t have docs available yet.
I think @drbenvincent linked notebook will already work because using return_inferencedata=True has already been updated to use the new conversion method under the hood, but you should still expect a bumpy ride when using PyMC3 4.x and you should see a warning about it being experimental for now at import time.