issue_comments: 442902327

I broadly agree with @benbovy 's proposal.

One question that I think is worth being clear on is what additional contracts do multiple indexes on a dimension have over individual indexes?

e.g. re: Coordinates: * level_1 (x) object 'a' 'a' 'b' 'b' * level_2 (x) int64 1 2 1 2 Multi-indexes: pandas.MultiIndex [level_1, level_2]

Am I right in thinking the Multi-indexes is only a helpful note to users, rather than conveying anything about how data is accessed?

@fujiisoup 's poses a good case of this question:

ds.sel(multi=list_of_pairs) can probably be replaced by ds.sel(x=..., y=...), but how about reindex along MultiIndex?

(and separately, I think we can do much of this before adding the ability to set custom indexes, which would be cool but further from where we are, I think)