input: Write a python function to calculate the area and perimeter of rectangles using the Rectangle class.
  assert (Rectangle(3, 4).get_area(), Rectangle(3, 4).get_perimeter()) == (12, 14)
  assert (Rectangle(5, 6).get_area(), Rectangle(5, 6).get_perimeter()) == (30, 22)
  assert (Rectangle(7, 8).get_area(), Rectangle(7, 8).get_perimeter()) == (56, 30)
output: class Rectangle:
      def __init__(self, length, width):
          self.length = length
          self.width = width
      
      def get_area(self):
          return self.length * self.width
      
      def get_perimeter(self):
          return 2 * (self.length + self.width)