input: Write a python function to calculate the area and perimeter of a rectangle using a class.
  assert Rectangle(4, 5).area() == 20
  assert Rectangle(4, 5).perimeter() == 18
  assert Rectangle(6, 7).area() == 42
  assert Rectangle(6, 7).perimeter() == 26
output: class Rectangle:
      def __init__(self, width, height):
          self.width = width
          self.height = height
  
      def area(self):
          return self.width * self.height
  
      def perimeter(self):
          return 2 * (self.width + self.height)