Return (parent, start, stop) triple with
Any of the three return values may equal None.
abjad> t = Staff(construct.scale(6))
abjad> print t.format
\new Staff {
c'8
d'8
e'8
f'8
g'8
a'8
}
abjad> leaves = t[-2:]
abjad> leaves
[Note(g', 8), Note(a', 8)]
abjad> parenttools.get_with_indices(leaves)
(Staff{6}, 4, 5)