docs: public void cancel(long orderId, long size) {
      Order order = orders.get(orderId);
      if (order == null) {
        return;
      }
  
      long remainingQuantity = order.size();
  
      if (size >= remainingQuantity) {
        return;
      }
  
      if (size > 0) {
        order.resize(size);
      } else {
        delete(order);
        orders.remove(orderId);
      }
  
      cancelListener.onNext(new CancelOrder(orderId, remainingQuantity - size, size));
    }