New in version 2.0.
Get exactly one annotation attached to component:
abjad> staff = Staff("c'8 d'8 e'8 f'8")
abjad> marktools.Annotation('special information')(staff[0])
Annotation('special information')(c'8)
abjad> f(staff)
\new Staff {
c'8
d'8
e'8
f'8
}
abjad> marktools.get_annotation_attached_to_component(staff[0])
Annotation('special information')(c'8)
Return one annotation.
Raise missing mark error when no annotation is attached.
Raise extra mark error when more than one annotation is attached.