New in version 2.0.
Change sequence to period of rotation:
abjad> from abjad.tools import sequencetools
abjad> sequencetools.get_sequence_period_of_rotation([1, 2, 3, 1, 2, 3], 1)
3
abjad> sequencetools.get_sequence_period_of_rotation([1, 2, 3, 1, 2, 3], 2)
3
abjad> sequencetools.get_sequence_period_of_rotation([1, 2, 3, 1, 2, 3], 3)
1
Return positive integer.