code: def Result(self, res):
          
          if isinstance(res, str):
              text = res
          elif res:
              text = "yes"
          else:
              text = "no"
  
          if self.did_show_result == 0:
              # Didn't show result yet, do it now.
              self.Display(text + "\n")
              self.did_show_result = 1
docs: Inform about the result of the test. If res is not a string, displays
          'yes' or 'no' depending on whether res is evaluated as true or false.
          The result is only displayed when self.did_show_result is not set.