docs: public List<Stanza> getCollectedStanzasAfterCancelled() {
          if (!cancelled) {
              throw new IllegalStateException("Stanza collector was not yet cancelled");
          }
  
          if (collectedCache == null) {
              collectedCache = new ArrayList<>(getCollectedCount());
              collectedCache.addAll(resultQueue);
          }
  
          return collectedCache;
      }