code: def test_efi_ext(self):
      self.data.ta.efi(append=True)
      self.assertIsInstance(self.data, DataFrame)
      self.assertEqual(self.data.columns[-1], "EFI_13")
  
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 TestVolumeExtension obj's underlying member method code with example usage: obj.test_efi_ext() without return types