List basebackups from an object store

def list_basebackups(self, arg):
        """List basebackups from an object store"""
        self.config = config.read_json_config_file(arg.config, check_commands=False, check_pgdata=False)
        site = config.get_site_from_config(self.config, arg.site)
        self.storage = self._get_object_storage(site, pgdata=None)
        self.storage.show_basebackup_list(verbose=arg.verbose)