New in version 2.3.
Get clef marks attached to component:
abjad> staff = Staff("c'8 d'8 e'8 f'8")
abjad> contexttools.ClefMark('treble')(staff)
ClefMark('treble')(Staff{4})
abjad> f(staff)
\new Staff {
\clef "treble"
c'8
d'8
e'8
f'8
}
abjad> contexttools.get_clef_marks_attached_to_component(staff)
(ClefMark('treble')(Staff{4}),)
Return tuple of zero or more clef marks.