Function cancellable_order_statuses_set 

pub fn cancellable_order_statuses_set() -> &'static AHashSet<OrderStatus>

Returns a cached AHashSet of cancellable order statuses for O(1) lookups.

For the small set (4 elements), using CANCELLABLE_ORDER_STATUSES.contains() may be equally fast due to better cache locality. Use this function when you need set operations or are building HashSet-based filters.

Note: This is a module-level convenience function. You can also use OrderStatus::cancellable_statuses_set() directly.