docs: private void handleLastFrame(AbstractFramedStreamSourceChannel newChannel) {
          //make a defensive copy
          Set<AbstractFramedStreamSourceChannel<C, R, S>> receivers = new HashSet<>(getReceivers());
          for(AbstractFramedStreamSourceChannel<C, R, S> r : receivers) {
              if(r != newChannel) {
                  r.markStreamBroken();
              }
          }
      }