At first glance, this seems to just be extra typing, but it's actually faster by 16% on CPython due to the implementation of .join() doing 2 passes on input if passed a generator.
From Trey Hunner: 'I do know that it's not possible to do 2 passes over a generator (since it'd be exhausted after the first pass) so from my understanding, the generator version requires an extra step of storing all the items in a list first.'
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