Return the interval class vector of pitches as a Python dictionary.
The interval vector implemented here gives the number of i0, ..., i6 between the n**2 - n pairs of pitches taken without respect for order.
abjad> chord = Chord([0, 2, 11], (1, 4))
abjad> vector = pitchtools.get_interval_class_vector(chord.pitches)
abjad> for i in range(7):
... print '\t%s\t%s' % (i, vector[i])
...
0 0
1 1
2 1
3 1
4 0
5 0
6 0
abjad> staff = Staff(construct.scale(4) + construct.scale(4) + construct.scale(4))
abjad> pitches = pitchtools.get_pitches(staff)
abjad> vector = pitchtools.get_interval_class_vector(pitches)
abjad> for i in range(7):
... print '\t%s\t%s' % (i, vector[i])
...
0 12
1 9
2 18
3 9
4 9
5 9
6 0