Implement the Factory Method design pattern.

The Factory Method is a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to decide which class to instantiate. Instead of calling a constructor directly, objects are created by calling a factory method.

You are given code that includes several vehicle types (Car, Bike, Truck) and their respective factory classes. Complete the factory method implementation so that each factory returns the correct vehicle type.

Example:

carFactory = CarFactory()
truckFactory = TruckFactory()
bikeFactory = BikeFactory()

myCar = carFactory.createVehicle()
myTruck = truckFactory.createVehicle()
myBike = bikeFactory.createVehicle()

myCar.getType() # "Car"
myTruck.getType() # "Truck"
myBike.getType() # "Bike"

How the tests work: each test runs the listed statements against your factories; the expected output is what every statement evaluates to (null for assignments).