input: Write a function to create a Python class named Car that stores and processes data related to a Car object. The class should have an initializer that takes four parameters: make, model, color, and mileage. It should also include two methods, accelerate and decelerate, which update the speed of the car.
  
  
  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
  
  assert Car("Toyota", "Camry", "Red", 50000).make == "Toyota"
  assert Car("Ford", "Mustang", "Blue", 30000).model == "Mustang"
  assert Car("Honda", "Civic", "White", 20000).color == "White"
  assert Car("Tesla", "Model S", "Black", 10000).mileage == 10000
  
  car = Car("BMW", "X5", "Silver", 40000)
  car.accelerate(60)
  assert car.speed == 60
  car.decelerate(30)
  assert car.speed == 30
  
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
  