New in version 2.0.
Change duration_tokens to rationals:
abjad> from abjad.tools import durationtools
abjad> durationtools.duration_tokens_to_rationals([Fraction(2, 4), 3, '8.', (5, 16)])
[Fraction(1, 2), Fraction(3, 1), Fraction(3, 16), Fraction(5, 16)]
Return new object of duration_tokens type.