def on_cleanup_error(function, path, excinfo):
                click.secho("warning: failed to remove file or directory: {}\n"
                            "please delete it manually.".format(path),
                            fg="red")
def serialize(self, value, display=False):
        if value is True:
            return "true"
        elif value in (False, None):
            return "false"
        else:
            raise ValueError(f"{value!r} is not a boolean")