input: Write a function to create a Car class in Python that stores and processes data related to a car object. The class should have an initializer to set the make, model, color, and mileage of the car, and it should have methods to accelerate and decelerate the car.
  assert Car("Toyota", "Camry", "Red", 5000).make=="Toyota"
  assert Car("Honda", "Accord", "Blue", 7500).model=="Accord"
  assert Car("Ford", "Mustang", "Black", 10000).color=="Black"
  assert Car("Tesla", "Model S", "White", 2500).mileage==2500
  car = Car("Audi", "A4", "Gray", 5000)
  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, amount):
          self.speed += amount
  
      def decelerate(self, amount):
          self.speed -= amount