code: def test_sessions(self):
      sessions = self.reader.sessions
  
      self.assertEqual(self.NUM_SESSIONS, len(sessions))
      self.assertEqual(self.START_DATE, sessions[0])
      self.assertEqual(self.END_DATE, sessions[-1])
  
file_path: catalyst/tests/test_panel_bar_reader.py
imports: from itertools import permutations, product
  import numpy
  import pandas
  from catalyst.data.us_equity_pricing import PanelBarReader
  from catalyst.testing import ExplodingObject
  from catalyst.testing.fixtures import WithAssetFinder, CatalystTestCase
  from catalyst.utils.calendars import get_calendar
label_desc: Use image node_id 4 for calling the WithPanelBarReader obj's underlying member method code with example usage: obj.test_sessions() without return types