code: def calc_trade_days_by_joinquant(self, start_day, end_day):
      dates = jq.get_trade_days(start_day, end_day)
      str_dates = [date2str(dt) for dt in dates]
      return str_dates
  
file_path: FinRL/finrl/meta/data_processors/processor_joinquant.py
imports: from __future__ import annotations
  import copy
  import os
  import jqdatasdk
  import numpy
  import pandas
  from func import calc_all_filenames
  from func import date2str
  from func import remove_all_files
label_desc: Use image node_id 5 for calling the JoinQuantEngineer obj's underlying member method code with example usage: obj.calc_trade_days_by_joinquant(start_day, end_day) and returns: str_dates