input: Write a python function to change the direction of a car object and verify the change using assertions.
  ```python
  class Car:
      # Initializer for the car
      def __init__(self, speed, direction):
          self.speed = speed
          self.direction = direction
  
      # Change direction of the car
      def change_direction(self, direction):
          self.direction = direction
  
  # Test cases
  car = Car(60, 'north')
  car.change_direction('east')
  assert car.direction == 'east'
  
  car.change_direction('west')
  assert car.direction == 'west'
  
  car.change_direction('south')
  assert car.direction == 'south'
output: class Car:
      # Initializer for the car
      def __init__(self, speed, direction):
          self.speed = speed
          self.direction = direction
  
      # Change direction of the car
      def change_direction(self, direction):
          self.direction = direction
  
  # Test cases
  car = Car(60, 'north')
  car.change_direction('east')
  assert car.direction == 'east'
  
  car.change_direction('west')
  assert car.direction == 'west'
  
  car.change_direction('south')
  assert car.direction == 'south'