class_docstr: Manager for trading calendar
      - BaseStrategy and BaseExecutor will use it
docstr: Get the start_time and end_time for trading
docstr_tok: ["Get","the","start_time","and","end_time","for","trading"]
code: def get_all_time(self) -> Tuple[pd.Timestamp, pd.Timestamp]:
      """Get the start_time and end_time for trading"""
      return self.start_time, self.end_time
  
imports: from __future__ import annotations
  from abc import abstractmethod
  from typing import Any, Set, Tuple, TYPE_CHECKING, Union
  import numpy
  from qlib.utils.time import epsilon_change
  import warnings
  import pandas
  from ..data.data import Cal
label_desc: Use image node_id 10 for calling the TradeCalendarManager obj's underlying member method code with example usage: obj.get_all_time() and returns: self,  self