def Result(self, res):
        """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.
        """
        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
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.