class_docstr: Exchange calendar for the CBOE Futures Exchange (CFE).
  
  http://cfe.cboe.com/aboutcfe/expirationcalendar.aspx
  
  Open Time: 8:30am, America/Chicago
  Close Time: 3:15pm, America/Chicago
  
  (We are ignoring extended trading hours for now)
code: def tz(self):
      return timezone("America/Chicago")
  
file_path: catalyst/catalyst/utils/calendars/exchange_calendar_cfe.py
imports: from datetime import time
  from itertools import chain
  from pandas.tseries.holiday import USPresidentsDay, USLaborDay, USThanksgivingDay, GoodFriday
  from pytz import timezone
  from catalyst.utils.calendars import TradingCalendar
  from catalyst.utils.calendars.trading_calendar import HolidayCalendar
  from catalyst.utils.calendars.us_holidays import USMartinLutherKingJrAfter1998, USMemorialDay, USBlackFridayInOrAfter1993, USNewYearsDay, USIndependenceDay, Christmas, HurricaneSandyClosings, USNationalDaysofMourning
label_desc: Use image node_id 2 for calling the CFEExchangeCalendar obj's underlying member method code with example usage: obj.tz() and returns: timezone