New in version 2.0.
Get effective context mark of klass from component:
abjad> staff = Staff("c'8 d'8 e'8 f'8")
abjad> contexttools.TimeSignatureMark((4, 8))(staff)
TimeSignatureMark((4, 8))(Staff{4})
abjad> f(staff)
\new Staff {
\time 4/8
c'8
d'8
e'8
f'8
}
abjad> contexttools.get_effective_context_mark(staff[0], contexttools.TimeSignatureMark)
TimeSignatureMark((4, 8))(Staff{4})
Return context mark or none.