code: def test_sessions(self):
      sessions = self.reader.sessions
      self.assertEqual(
          21, len(sessions), "There should be 21 sessions in 2015-11."
      )
      self.assertEqual(
          pd.Timestamp("2015-11-02", tz="UTC"), sessions[0]
      )
      self.assertEqual(
          pd.Timestamp("2015-11-30", tz="UTC"), sessions[-1]
      )
  
imports: from collections import OrderedDict
  from numbers import Real
  from nose_parameterized import parameterized
  from numpy.testing import assert_almost_equal
  from numpy import nan, array, full, isnan
  import pandas
  from pandas import DataFrame
  from six import iteritems
  from catalyst.data.resample import minute_frame_to_session_frame, DailyHistoryAggregator, MinuteResampleSessionBarReader, ReindexMinuteBarReader, ReindexSessionBarReader
  from catalyst.testing import parameter_space
  from catalyst.testing.fixtures import WithEquityMinuteBarData, WithBcolzEquityMinuteBarReader, WithBcolzEquityDailyBarReader, WithBcolzFutureMinuteBarReader, CatalystTestCase
label_desc: Use image node_id 8 for calling the TestReindexSessionBars obj's underlying member method code with example usage: obj.test_sessions() without return types