code: def test_not_implemented(self):
      with self.assertRaises(NotImplementedError):
          super(Always, Always()).should_trigger("a")
  
imports: import datetime
  from inspect import isabstract
  import random
  from unittest import TestCase
  import warnings
  from nose_parameterized import parameterized
  import pandas
  from six import iteritems
  from six.moves import range, map
  from trading_calendars import get_calendar
  import zipline.utils.events
  from zipline.utils.events import EventRule, StatelessRule, Always, Never, AfterOpen, ComposedRule, BeforeClose, NotHalfDay, NthTradingDayOfWeek, NDaysBeforeLastTradingDayOfWeek, NthTradingDayOfMonth, NDaysBeforeLastTradingDayOfMonth, StatefulRule, OncePerDay, _build_offset, _build_date, _build_time, EventManager, Event, MAX_MONTH_RANGE, MAX_WEEK_RANGE, TradingDayOfMonthRule, TradingDayOfWeekRule
label_desc: Use image node_id 2 for calling the TestEventRule obj's underlying member method code with example usage: obj.test_not_implemented() without return types