def list(self):
        """
        List all backups as WorkspaceBackup objects, sorted descending by lastmod.
        """
        backups = []
        for d in glob(join(self.backup_directory, '*')):
            backups.append(WorkspaceBackup.from_path(d))
        backups.sort(key=lambda b: b.lastmod, reverse=True)
        return backups
List all backups as WorkspaceBackup objects, sorted descending by lastmod.