input: Write a python function to calculate the area of a rectangle using a class.
  assert Rectangle(5, 3).get_area() == 15
  assert Rectangle(10, 2).get_area() == 20
  assert Rectangle(7, 7).get_area() == 49
output: class Rectangle:
      def __init__(self, width, height):
          self.width = width
          self.height = height
  
      def get_area(self):
          return self.width * self.height