API GetContainerItemID

Returns the item ID in a container slot.
 itemId = GetContainerItemID(bag, slot)
==Arguments==
:;bag: (BagID) - Index of the bag to query.
:;slot: - Index of the slot within the bag to query; ascending from 1.
==Returns==
:;itemId: - item ID of the item held in the container slot, nil if there is no item in the container slot.