input: Write a python function to calculate the area of a square using a class that inherits from a rectangle class.
  assert Square(4).get_area() == 16
  assert Square(5).get_area() == 25
  assert Square(0).get_area() == 0
output: class Rectangle:
      def __init__(self, width, height):
          self.width = width
          self.height = height
  
      def get_area(self):
          return self.width * self.height
  
  class Square(Rectangle):
      def __init__(self, side_length):
          super().__init__(side_length, side_length)