code: def _write_calendar(self, values: Iterable[CalVT], mode: str = "wb"):
      with self.uri.open(mode=mode) as fp:
          np.savetxt(fp, values, fmt="%s", encoding="utf-8")
  
imports: import struct
  from pathlib import Path
  from typing import Iterable, Union, Dict, Mapping, Tuple, List
  import numpy
  import pandas
  from qlib.utils.time import Freq
  from qlib.utils.resam import resam_calendar
  from qlib.config import C
  from qlib.data.cache import H
  from qlib.log import get_module_logger
  from qlib.data.storage import CalendarStorage, InstrumentStorage, FeatureStorage, CalVT, InstKT, InstVT
label_desc: Use image node_id 5 for calling the FileCalendarStorage obj's underlying member method code with example usage: obj._write_calendar(values, mode) without return types