code: private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
  		// Write out any hidden stuff
  		s.defaultWriteObject();
  
  		// Write out Comparator
  		s.writeObject(m.comparator());
  
  		// Write out size
  		s.writeInt(m.size());
  
  		// Write out all elements in the proper order.
  		for (Iterator<E> i = m.keySet().iterator(); i.hasNext();)
  			s.writeObject(i.next());
  	}
docs: Save the state of the {@code OTreeSet} instance to a stream (that is, serialize it).
  
  @serialData Emits the comparator used to order this set, or {@code null} if it obeys its elements' natural ordering (Object),
  followed by the size of the set (the number of elements it contains) (int), followed by all of its elements (each
  an Object) in order (as determined by the set's Comparator, or by the elements' natural ordering if the set has no
  Comparator).