sS detectInterestingLines_suffix = "<< detect";

static BitSet detectInterestingLines(L<S> log) {
  new BitSet bs;
  for (int i = 0; i < l(log); i++)
    if (endsWith(log.get(i), detectInterestingLines_suffix)) {
      bs.set(i);
      log.set(i, dropSuffixAndTrim(detectInterestingLines_suffix, log.get(i)));
    }
  ret bs;
}