Return number of the form 1/2**n that is either just greater, or just less, than prolated_duration, according to ‘prolation’.
Intended to find written duration of notes inside tuplet.
durtools.naive_prolated_to_writtenRational(3, 80), ‘diminution’) Rational(1, 32)
durtools.naive_prolated_to_writtenRational(3, 80), ‘augmentation’) Rational(1, 16)