code: public StackTraceElement[] filter(StackTraceElement[] target, boolean keepTop) {
          //TODO: profile
          //TODO: investigate "keepTop" commit history - no effect!
          final List<StackTraceElement> filtered = new ArrayList<StackTraceElement>();
          for (StackTraceElement element : target) {
              if (CLEANER.isIn(element)) {
                  filtered.add(element);
              }
          }
          StackTraceElement[] result = new StackTraceElement[filtered.size()];
          return filtered.toArray(result);
      }
docs: Example how the filter works (+/- means good/bad):
  [a+, b+, c-, d+, e+, f-, g+] -> [a+, b+, d+, e+, g+]
  Basically removes all bad from the middle.
  <strike>If any good are in the middle of bad those are also removed.</strike>