input: Write a function to create a Car class in Python that stores and processes data for a Car object. The class should have attributes for the make, model, color, and mileage of the car, and methods to accelerate and decelerate the car.
  class Car:
      def __init__(self, make, model, color, mileage):
          self.make = make
          self.model = self.model
          self.color = self.color
          self.mileage = self.mileage
  
      def accelerate(self, speed):
          self.speed = speed
  
      def decelerate(self, speed"):
          self.speed = speed
  
  assert Car("Toyota", "Corolla", "Silver", 50000).make == "Toyota"
  assert Car("Honda", "Civic", "Blue", 30000).model == "Civic"
  assert Car("Tesla", "Model S", "Red", 10000).color == "Red"
  assert Car("Ford", "Mustang", "Black", 70000).mileage ==  70000
  my_car = Car("BMW", "X5", "White", 40000)
  my_car.accelerate(60)
  assert my_car.speed == 60
  my_car.decelerate(30)
  assert my_car.speed == 90
output: 
  class Car:
      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
  