docs: @SuppressWarnings("unchecked")
      // TODO: Consider removing this method as it is hardly ever useful.
      public synchronized <P extends Stanza> P nextResultBlockForever() throws InterruptedException {
          throwIfCancelled();
  
          while (true) {
              P res = (P) resultQueue.poll();
              if (res != null) {
                  return res;
              }
              if (cancelled) {
                  return null;
              }
              wait();
          }
      }