docstr: get companies changes
  
  Returns
  -------
      pd.DataFrame:
          symbol      date        type
          SH600000  2019-11-11    add
          SH600000  2020-11-10    remove
      dtypes:
          symbol: str
          date: pd.Timestamp
          type: str, value from ["add", "remove"]
docstr_tok: ["get","companies","changes","Returns","--","--","--","-","pd.DataFrame",":","symbol","date","type","SH600000","2019-11-11","add","SH600000","2020-11-10","remove","dtypes",":","symbol",":","str","date",":","pd.Timestamp","type",":","str",",","value","from","[","``","add","''",",","``","remove","''","]"]
code: def get_changes(self) -> pd.DataFrame:
      """get companies changes
  
      Returns
      -------
          pd.DataFrame:
              symbol      date        type
              SH600000  2019-11-11    add
              SH600000  2020-11-10    remove
          dtypes:
              symbol: str
              date: pd.Timestamp
              type: str, value from ["add", "remove"]
      """
      raise NotImplementedError("rewrite get_changes")
  
imports: import abc
  from functools import partial
  import sys
  from pathlib import Path
  from concurrent.futures import ThreadPoolExecutor
  from typing import List
  import fire
  import requests
  import pandas
  from tqdm import tqdm
  from loguru import logger
  from data_collector.index import IndexBase
  from data_collector.utils import deco_retry, get_calendar_list, get_trading_date_by_shift
  from data_collector.utils import get_instruments
label_desc: Use image node_id 3 for calling the WIKIIndex obj's underlying member method code with example usage: obj.get_changes() without return types