My preferred way of thinking of "yield from" is as a simple
refactoring tool: "Gee, this generator is getting kind of long and
unwieldy. I'll move this piece out into a separate generator, and use
yield from to invoke it" or "Hmm, I keep using this same sequence of 3
or 4 operations. I guess I'll move them out to a separate generator
and use yield from to invoke it in the appropriate places".