input: class Rectangle:
      def __init__(self, length: float, width: float):
          self.length = length
          self.width = width
  
      def area(self) -> float:
          """ Calculate and return the area of the rectangle.
          >>> rect = Rectangle(5, 10)
          >>> rect.area()
          50
          >>> rect = Rectangle(7.5, 3)
          >>> rect.area()
          22.5
          """
          return self.length * self.width
output:     def perimeter(self) -> float:
          """ Calculate and return the perimeter of the rectangle.
          >>> rect = Rectangle(5, 10)
          >>> rect.perimeter()
          30
          >>> rect = Rectangle(7.5, 3)
          >>> rect.perimeter()
          21.0
          """
          return 2 * (self.length + self.width)