Swift Playground “Learn to Code 2” expert command “turnLockUp()”

There is a command “turnLockUp()” in expert. But I don’t know how to use. Run it before it step on the lock? Or run it when it is on the lock? Can anyone tell me?

Expert.turnLockUp doesn’t seem to work in 5.1 Learn to Code 2.

Swift Playground “Learn to Code 2” expert command “turnLockUp()”
 
 
Q