Py3 TODO comments in core.Universe

[IAlibay]

Just having a look through core.Universe and I'm noticing there's a lot of comments tagged as "Py3 TODO"
e.g.

mdanalysis/package/MDAnalysis/core/universe.py

Lines 141 to 142 in 45e56e8

	# py3 TODO
	#def _resolve_formats(*coordinates, format=None, topology_format=None):

It's unclear to me what are intended by these, but now that we are solely py3+ we should either implement them or remove the comments?

[richardjgowers]

It might be argument unpacking changes that are py3 specific. I think you previously couldn't have named kwargs after a variable length list of args. I think when @lilyminium was reworking Universe creation she ran into this a bit if you want to find the PR

[IAlibay]

I see, this is related to #2322, I don't think there's another opened issue for this, so I'll add it to the 2.0 milestone.