code: def save_calendars(self, calendars_data: list):
      self._calendars_dir.mkdir(parents=True, exist_ok=True)
      calendars_path = str(
          self._calendars_dir.joinpath(f"{self.freq}.txt")
          .expanduser()
          .resolve()
      )
      result_calendars_list = [
          self._format_datetime(x) for x in calendars_data
      ]
      np.savetxt(
          calendars_path,
          result_calendars_list,
          fmt="%s",
          encoding="utf-8",
      )
  
imports: import abc
  import shutil
  import traceback
  from pathlib import Path
  from typing import Iterable, List, Union
  from functools import partial
  from concurrent.futures import ThreadPoolExecutor, as_completed, ProcessPoolExecutor
  import fire
  import numpy
  import pandas
  from tqdm import tqdm
  from loguru import logger
  from qlib.utils import fname_to_code, code_to_fname
label_desc: Use image node_id 10 for calling the DumpDataBase obj's underlying member method code with example usage: obj.save_calendars(calendars_data) without return types