input: 
  def rectangle(length: float, width: float) -> float:
      """ Calculate the area of a rectangle given its length and width.
      >>> rectangle(5.0, 3.0)
      15.0
      >>> rectangle(7.0, 2.0)
      14.0
      >>> rectangle(4.0, 4.0)
      16.0
      """
      return length * width
  
output:     return length * width