docs: public Evaluator addGroupSubscriptions(String group, List<Subscription> subs) {
      List<Subscription> oldSubs = subscriptions.put(group, subs);
      if (oldSubs == null) {
        LOGGER.debug("added group {} with {} subscriptions", group, subs.size());
      } else {
        LOGGER.debug("updated group {}, {} subscriptions before, {} subscriptions now",
            group, oldSubs.size(), subs.size());
      }
      return this;
    }