Fixed options, i_options and callable can all be merged into a single callable either yielding depending on seq or yelding constant values

You can also meege it with filters. So you will have only one genetator. All the logic be inside that generator.

You don't need to pass index as separate argument. You can just use length of seq

use empty seq instead of None

todoL use 0 in lookback constraint instead of candidate constraint

#opseq