input: Write a python function to create a description of a car using the Car class.
  assert Car('Toyota', 'Camry', 2020).description() == 'This car is a 2020 Toyota Camry'
  assert Car('Honda', 'Civic', 2018).description() == 'This car is a 2018 Honda Civic'
  assert Car('Ford', 'Mustang', 1965).description() == 'This car is a 1965 Ford Mustang'
output: class Car:
      def __init__(self, make, model, year):
          self.make = make
          self.model = model
          self.year = year
  
      def description(self):
          return f'This car is a {self.year} {self.make} {self.model}'