code: def test_add_event_prepend(self):
      self.em.add_event(self.event1)
      self.em.add_event(self.event2, prepend=True)
      self.assertEqual([self.event2, self.event1], self.em._events)
  
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 3 for calling the TestEventManager obj's underlying member method code with example usage: obj.test_add_event_prepend() without return types