docs: public boolean addIfOpen(E element) {
  		requireNonNull(element);
  
  		lock.lock();
  		try {
  			if (open) {
  				elements.addLast(element);
  				if (elements.size() == 1) {
  					nonEmpty.signalAll();
  				}
  			}
  			return open;
  		} finally {
  			lock.unlock();
  		}
  	}