Modify the filename of a log file when rotating.

        This is provided so that a custom filename can be provided.

        :param default_name: The default name for the log file.

def rotation_filename(self, default_name: str) -> str:
        """
        Modify the filename of a log file when rotating.

        This is provided so that a custom filename can be provided.

        :param default_name: The default name for the log file.
        """
        if self.namer is None:
            return default_name

        return self.namer(default_name)