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