How LockerManagerChange class is used?

[ntalbs]

ood-interview/shipping_locker/shipping_locker_deep_dive/LockerManagerChange.java

Line 9 in 29b9ddc

class LockerManagerChange {

Is it a drop-in replacement for LockerManager or intended to be used in LockerManager?

assignPackage method in LockerManager has two parameters and uses Site internally to assign a package. However, assignPackage in LockerManagerChange has only one parameter, and the calls assignLockerToPackage private method, which just returns null. Seems like the explanation in the book about this is incomplete.