Call set_display_mode on items in self.comments with given args.

        :arg mytz:      A pytz.timezone object.

        :arg fmt="%Y-%m-%d%H:%M:%S%Z%z":   Optional format string.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        PURPOSE:        Call set_display_mode(mytz, fmt) for everything in
                        self.comments.

def set_display_mode(self, mytz, fmt="%Y-%m-%d %H:%M:%S %Z%z"):
        """Call set_display_mode on items in self.comments with given args.

        :arg mytz:      A pytz.timezone object.

        :arg fmt="%Y-%m-%d%H:%M:%S%Z%z":   Optional format string.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        PURPOSE:        Call set_display_mode(mytz, fmt) for everything in
                        self.comments.

        """
        for item in self.comments:
            item.set_display_mode(mytz, fmt)