New in version 2.0.
Iterate containers forward in expr:
abjad> staff = Staff([Voice("c'8 d'8"), Voice("e'8 f'8 g'8")])
abjad> Tuplet(Fraction(2, 3), staff[1][:])
Tuplet(2/3, [e'8, f'8, g'8])
abjad> staff.is_parallel = True
abjad> f(staff)
\new Staff <<
\new Voice {
c'8
d'8
}
\new Voice {
\times 2/3 {
e'8
f'8
g'8
}
}
>>
abjad> for x in containertools.iterate_containers_forward_in_expr(staff):
... x
Staff<<2>>
Voice{2}
Voice{1}
Tuplet(2/3, [e'8, f'8, g'8])
Ignore threads.
Return generator.