func (o *OrderBook) AddOrder(order *common.Order) error {
tradePairKey := order.TradePair().Key()
orders := o.getArrivalAddOrders(tradePairKey)
func (o *OrderBook) AddOrder(order *common.Order) error {
tradePairKey := order.TradePair().Key()
orders := o.getArrivalAddOrders(tradePairKey)