static Set<S> applyAttractors(L<? extends Attractor> rules, S s) {
  ret concatListsToCISet(map(rules, rule ->
    rule.matches(s) ? getStringEmits(rule) : null
  );
}

static Set<S> applyAttractors(L<? extends Attractor> rules, Collection<S> inputs, O... _) {
  Set<S> out = cloneLinkedCISet(inputs);
  for unnull (S input : inputs)
    functionReturningList_transitiveHull_ciSet(func(S s) -> Collection<S> { applyAttractors(rules, s) }, input, optPar seen(_, out));
  ret out;
}

Began life as a copy of #1023191