New in version 2.0.
Change expr to melodic chromatic interval segment:
abjad> staff = Staff("c'8 d'8 e'8 f'8 g'8 a'8 b'8 c''8")
abjad> pitchtools.expr_to_melodic_chromatic_interval_segment(staff)
MelodicChromaticIntervalSegment(+2, +2, +1, +2, +2, +2, +1)
Return melodic chromatic interval segment.