code: def write_calendar(self, calendar: Iterable):
      calendars_list = [
          self._format_datetime(x)
          for x in sorted(set(self.calendar_list + calendar))
      ]
      np.savetxt(
          self.future_path, calendars_list, fmt="%s", encoding="utf-8"
      )
  
imports: import abc
  import importlib
  from pathlib import Path
  from typing import Union, Iterable, List
  import fire
  import numpy
  import pandas
  import baostock
  from loguru import logger
label_desc: Use image node_id 4 for calling the CollectorFutureCalendar obj's underlying member method code with example usage: obj.write_calendar(calendar) without return types