input:     Write a function to create a Car class in Python that stores and processes data related to a Car object. The class should include an initializer method to set the make, model, color, and mileage of the car, and should also include methods to accelerate and decelerate 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 type(Car("Toyota", "Camry", "Red", 50000)) == Car
      assert Car("Honda", "Civic", "Blue", 30000).make == "Honda"
      assert Car("Ford", "Mustang", "Yellow", 70000).model == "Mustang"
      assert Car("Tesla", "Model S", "Black", 10000).color == "Black"
      car = Car("BMW", "X5", "White", 40000)
      car.accelerate(50)
      assert car.speed == 50
      car.decelerate(30)
      assert car.speed == 20
      car.decelerate(20)
      assert car.speed == 0
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
  