code: @Override
  	public Mono<Void> save(MongoSession session) {
  
  		DBObject dbObject = convertToDBObject(this.mongoSessionConverter, session);
  		if (dbObject != null) {
  			return this.mongoOperations.save(dbObject, this.collectionName).then();
  		} else {
  			return Mono.empty();
  		}
  	}
docs: Ensures the {@link MongoSession} created by {@link ReactiveSessionRepository#createSession()} is saved.
  <p>
  Some implementations may choose to save as the {@link MongoSession} is updated by returning a {@link MongoSession}
  that immediately persists any changes. In this case, this method may not actually do anything.
  </p>
  
  @param session the {@link MongoSession} to save