What is a circular sequence
For our purposes, a circular sequence is a sequence composed by a finite number of elements forming a ring.
Being circular, the first element of the sequence can be considered as also placed just after the last element.
from ring_seq import RingSeq
>>> RingSeq("ABC").apply_o(3)
'A'
And the last just before the first.
from ring_seq import RingSeq
>>> RingSeq("ABC").apply_o(-1)
'C'
So the "unrolling" of a circular sequence, both forth and backwards, can be assumed as theoretically infinite.
from ring_seq import RingSeq
>>> RingSeq("ABC").apply_o(30001)
'B'