WIP Import coords and dims from pymc3

[aseyboldt]

*Depends on pymc-devs/pymc#3551 *
This allows arviz to read dims and coords from pymc3 when they are defined.

[canyon289]

This looks great! Is it still in WIP and or do we need to add tests?

[ahartikainen]

Is this ready (I would like to get this in for the next release)

[canyon289]

Checking in on old PRs. Any possibility of bringing this over the line or should we close?

[OriolAbril]

I think this depends on a PR to PyMC3 that just got reactivated. We should probably revisit after pymc-devs/pymc#3551 has been merged and see if it would require any release magic/monkeypatching... cc @AlexAndorra @michaelosthege

If interesting, I can rebase the PR (I am quite up to date with changes in io_pymc3 and should not break any of the new changes while rebasing)

[AlexAndorra]

Indeed, I'm planning to review the PyMC PR in the coming days -- will keep you posted 😉
We're trying to merge the PR to have it in 3.9, so it should be resolved quite quickly.

[michaelosthege]

I resolved the conflicts in #1228. Testing with the PyMC3 PR branch now…
This PR can be closed.