docs: private boolean updateStreamBlacklist(Set<Tuple2<String, String>> processingBlacklist,
                                            Message message,
                                            Set<String> initialStreamIds) {
          boolean addedStreams = false;
          for (Stream stream : message.getStreams()) {
              if (!initialStreamIds.remove(stream.getId())) {
                  addedStreams = true;
              } else {
                  // only add pre-existing streams to blacklist, this has the effect of only adding already processed streams,
                  // not newly added ones.
                  processingBlacklist.add(tuple(message.getId(), stream.getId()));
              }
          }
          return addedStreams;
      }