code: def new_backup(self, src):
          
  
          backup_id_file = p.join(self.backup_dir, '.bk_idx')
          backup_num = file_or_default(backup_id_file, 1, int)
          backup_name = str(backup_num) + "_" + os.path.basename(src)
          backup_num += 1
  
          file_put_contents(backup_id_file, str(backup_num))
          return p.join(self.backup_dir, backup_name)
docs: Create a new backup file allocation