old_contents: class App():
      def __init__(self):
          self.var1 = 20
  
      def calculate(self):
          self.result = self.var1 * 4 + 2
  
      def retrieve(self):
          return self.result
  
  if __name__ == "__main__":
      app = App()
      app.calculate()
      print(app.retrieve)
  
new_contents: class App():
      def __init__(self):
          self.var1 = 15
  
      def calculate(self):
          self.result = self.var1 * 4 + 2
  
      def retrieve(self):
          return self.result
  
  if __name__ == "__main__":
      app = App()
      app.calculate()
      print(app.retrieve)
  
subject: make test successful