code: def testDuplicateBars(self):
      barFeed = yahoofeed.Feed()
      barFeed.addBarsFromCSV(
          FeedTestCase.TestInstrument,
          common.get_data_file_path("orcl-2000-yahoofinance.csv"),
      )
      barFeed.addBarsFromCSV(
          FeedTestCase.TestInstrument,
          common.get_data_file_path("orcl-2000-yahoofinance.csv"),
      )
      with self.assertRaisesRegexp(
          Exception, "Duplicate bars found for.*"
      ):
          barFeed.loadAll()
  
imports: import datetime
  from .None import common
  from .None import barfeed_test
  from .None import feed_test
  from pyalgotrade.utils import dt
  from pyalgotrade.barfeed import yahoofeed
  from pyalgotrade.barfeed import csvfeed
  from pyalgotrade import bar
  from pyalgotrade import marketsession
label_desc: Use image node_id 4 for calling the FeedTestCase obj's underlying member method code with example usage: obj.testDuplicateBars() without return types