we can also use any other methods since mid is point object in the definition of the method halfway see how the requirement to always use dot notation with attributes disambiguates the meaning of the attributes and ywe can always see whether the coordinates of point self or target are being referred to instances as return valueswhen you call an instance method ( func from an instance object ( inst )python automatically passes that instance object as the first argumentin addition to any other arguments that were passed in by the user in the example there are two classes vehicle and truckobject of class truck is passed as parameter to the method of class vehicle in method main(object of vehicle is created then the add_truck(method of class vehicle is called and object of truck class is passed as parameter exampleclass vehicledef __init__(self)self trucks [def add_truck(selftruck)self trucks append(truckclass truckdef __init__(selfcolor)self color color def __repr__(self)return "{}format(self colordef main() vehicle(for in 'red blue blacksplit() truck(tv add_truck(tprint( trucksif __name__ ="__main__"main(