New in version 2.0.
Get effective clef of 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> for note in staff:
... print note, contexttools.get_effective_clef(note)
...
c'8 ClefMark('treble')(Staff{4})
d'8 ClefMark('treble')(Staff{4})
e'8 ClefMark('treble')(Staff{4})
f'8 ClefMark('treble')(Staff{4})
Return clef mark or none.