code: def test_bbands_ext(self):
      self.data.ta.bbands(append=True)
      self.assertIsInstance(self.data, DataFrame)
      self.assertEqual(
          list(self.data.columns[-5:]),
          [
              "BBL_5_2.0",
              "BBM_5_2.0",
              "BBU_5_2.0",
              "BBB_5_2.0",
              "BBP_5_2.0",
          ],
      )
  
imports: from .config import sample_data
  from .context import pandas_ta
  from unittest import TestCase
  from pandas import DataFrame
label_desc: Use image node_id 8 for calling the TestVolatilityExtension obj's underlying member method code with example usage: obj.test_bbands_ext() without return types