input: 
  class Rectangle:
      """Represents a two-dimensional rectangle with a length and width.
      >>> rect = Rectangle(4, 5)
      >>> rect.area()
      20
      """
      def __init__(self, length: float, width: float):
          self.length = length
          self.width = width
  
      def area(self) -> float:
          return self.length * self.width
  
output:     
      def perimeter(self) -> float:
          return 2 * (self.length + self.width)
  