input: Write a function to create a class in Python that stores and processes data in a Car object. The class should have an initializer that takes make, model, color, and mileage as attributes. The class should also have methods for accelerating and decelerating the car. 
  
  class Car:
      def __init__(self, make, model, color, mileage):
          self.make = make
          self.model = model
          self.color = color
          self.mileage = mileage
  
      def accelerate(self, speed):
          self.speed = speed
  
      def decelerate(self, speed):
          self.speed = speed
  
  assert Car('Toyota', 'Corolla', 'Red', 50000).make == 'Toyota'
  assert Car('Honda', 'Civic', 'Blue', 60000).model == 'Civic'
  assert Car('Ford', 'Mustang', 'Yellow', 70000).color == 'Yellow'
  assert Car('Chevrolet', 'Cruze', 'Black', 80000).mileage == 80000
  
  car = Car('Audi', 'A4', 'White', 90000)
  car.accelerate(60)
  assert car.speed == 60
  car.decelerate(40)
  assert car.speed == 40
output: def __init__(self, make, model, color, mileage):
      self.make = make
      self.model = model
      self.color = color
      self.mileage = mileage
      self.speed = 0
  
  def accelerate(self, speed):
      self.speed += speed
  
  def decelerate(self, speed):
      self.speed -= speed