input: 
  class Rectangle:
      """A class to represent a two-dimensional rectangle with a length and width.
      It should have methods to calculate the area of the rectangle.
  
      >>> rect = Rectangle(5, 10)
      >>> rect.area()
      50
      >>> rect = Rectangle(3, 4)
      >>> rect.area()
      12
      """
      def __init__(self, length, width):
          self.length = length
          self.width = width
  
      def area(self):
          return self.length * self.width
  
output:     
      def perimeter(self):
          return 2 * (self.length + self.width)
  