input: Write a function that defines a Python class called Rectangle to represent a two-dimensional rectangle with a length and width. The class should have an initializer to set the length and width, and a method to calculate the area of the rectangle.
  
  class Rectangle:
      def __init__(self, length, width):
          self.length = length
          self.width = width
  
      def area(self):
          return self.length * self.width
  
  assert Rectangle(4, 5).area() == 20
  assert Rectangle(7, 3).area() == 21
  assert Rectangle(0, 5).area() == 0
  assert Rectangle(6, 0).area() == 0
  assert Rectangle(2, 2).area() == 4
output: class Rectangle:
      def __init__(self, length, width):
          self.length = length
          self.width = width
  
      def area(self):
          return self.length * self.width