docs: private Optional<ERETrigger> extractPossiblyAbsentTrigger(final Element xml, final String docid) {
      try {
        return Optional.of(extractTrigger(xml, docid));
      } catch (XMLUnexpectedInputException e) {
        e.printStackTrace();
        log.info("no trigger found for {}, error is {}", xml, e.toString());
      }
      return Optional.absent();
    }