Should Base.keys(ds) default to varnames(ds)

[lupemba]

Reading the documentation it looks like that varnames should be implemented for each AbstractDataset but my experience with MetopNative.jl is that CommonDataModel.jl relies more on Base.keys e.g. in the show method

CommonDataModel.jl/src/dataset.jl

Line 99 in e630054

varnames = keys(ds)

An easy fix for this could be to add varnames as the fallback method.

Base.keys(ds::AbstractDataset) = varnames(ds)

I might try to make a PR tomorrow.

[Alexander-Barth]

Yes, that is a good idea! Thanks!