New in version 2.0.
Retain sequence elements at indices mod period plus offset:
abjad> from abjad.tools import sequencetools
abjad> sequencetools.retain_sequence_elements_at_indices_cyclically(range(20), [0, 1], 5, 3)
[3, 4, 8, 9, 13, 14, 18, 19]
Ignore negative values in indices.
Return list.