code: def test_kc_ext(self):
      self.data.ta.kc(append=True)
      self.assertIsInstance(self.data, DataFrame)
      self.assertEqual(
          list(self.data.columns[-3:]),
          ["KCLe_20_2", "KCBe_20_2", "KCUe_20_2"],
      )
  
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 10 for calling the TestVolatilityExtension obj's underlying member method code with example usage: obj.test_kc_ext() without return types