Iterate expr. Slip each trivial tuplet in expr out of score.
Example:
abjad> t = FixedDurationTuplet((1, 4), construct.scale(3))
abjad> u = FixedDurationTuplet((1, 4), construct.scale(2))
abjad> s = Staff([t, u])
abjad> len(s)
2
abjad> s[0]
FixedDurationTuplet(1/4, [c'8, d'8, e'8])
abjad> s[1]
FixedDurationTuplet(1/4, [c'8, d'8])
abjad> tuplettools.slip_trivial(s)
abjad> len(s)
3
abjad> s[0]
FixedDurationTuplet(1/4, [c'8, d'8, e'8])
abjad> s[1]
Note(c', 8)
abjad> s[2]
Note(d', 8)
abjad> f(s)
\new Staff {
\times 2/3 {
c'8
d'8
e'8
}
c'8
d'8
}