New in version 2.0.
Negate sequence elements at indices cyclically according to period:
abjad> from abjad.tools import sequencetools
abjad> sequence = [1, 2, 3, 4, 5, -6, -7, -8, -9, -10]
abjad> sequencetools.negate_sequence_elements_cyclically(sequence, [0, 1, 2], 5)
[-1, -2, -3, 4, 5, 6, 7, 8, -9, -10]
Return newly constructed list.