input: Write a function to create a Python class called Rectangle to represent a two-dimensional rectangle with a length and width. The class should have a method called area that returns the area of the rectangle.
  
  assert Rectangle(4, 5).area()==20
  assert Rectangle(10, 2).area()==20
  assert Rectangle(3, 3).area()==9
  assert Rectangle(0, 5).area()==0
  assert Rectangle(7, 2).area()==14
output: class Rectangle:
      def __init__(self, length, width):
          self.length = length
          self.width = width
      
      def area(self):
          return self.length * self.width