Review: Parking Lot - The Exit Display PR

Your task

Review this pull request before it's merged. Read parkinglot/ParkingLot.java (in Python, parkinglot/parking_lot.py), click the margin next to each line with a problem, and say what kind of problem it is, how bad it is, and why. There are problems planted in this code - the count is shown above the code - and the review is graded on whether you find them without crying wolf.

The pull request

PR #214 - Show the plate at the exit gate

The exit gate's display now shows the plate a ticket was issued for (plateFor), and the new operations dashboard lists every spot on the level (getSpots). (Python: plate_for and the spots property.) Parking and unparking are unchanged.

What the lot must do

• parkVehicle(vehicle) puts the vehicle in a free spot of its size - MOTORCYCLE in SMALL, CAR in MEDIUM, BUS in LARGE - and returns a new ticket, or null (None) if none is free. In Python the methods are park_vehicle, unpark_vehicle and available_spots.
• unparkVehicle(ticket) frees that ticket's spot and returns true; an unknown ticket returns false and changes nothing. A ticket is good for one exit - the exit gate retries requests when the barrier is slow to answer.
• availableSpots(size) counts the free spots of that size.
• ParkingSpot (not in this PR) is a plain mutable class: getSize(), isOccupied(), setOccupied(boolean) - in Python the attributes size and occupied.