> if your collection isn't amenable to being generated by a simple expression like a map or fold, then you have to create a collection, prep the collection to be what you want it to be, then you return it.

This release added the ability to "yield" values via a generator fashion. It's called `unfold`, but will be renamed to `generate` in the next release: https://www.nushell.sh/commands/docs/unfold.html.