input: Write a function to create a class in Python that represents a Car object with attributes and methods for accelerating and decelerating. The class should include an initializer to set the make, model, color, and mileage of the car.
  def Car(make, model, color, mileage):
      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
      return Car(make, model, color, mileage)
  assert Car("Toyota", "Camry", "Red", 50000).make=="Toyota"
  assert Car("Ford", "Mustang", "Blue", 30000).model=="Mustang"
  assert Car("Honda", "Civic", "Silver", 20000).color=="Silver"
  assert Car("Chevrolet", "Malibu", "Black", 70000).mileage==70000
output: def Car(make, model, color, mileage):
      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
      return Car(make, model, color, mileage)