docs: public void add(long instrument, long orderId, Side side, long price, long size) {
      if (orders.containsKey(orderId)) {
        return;
      }
  
      OrderBook book = books.get(instrument);
      if (book == null) {
        return;
      }
  
      Order order = new Order(book, side, price, size);
  
      boolean bbo = book.add(side, price, size);
  
      orders.put(orderId, order);
  
      listener.update(book, bbo);
    }