code: def test_mad_ext(self):
      self.data.ta.mad(append=True)
      self.assertIsInstance(self.data, DataFrame)
      self.assertEqual(self.data.columns[-1], "MAD_30")
  
file_path: pandas-ta/tests/test_ext_indicator_statistics.py
imports: from .config import sample_data
  from .context import pandas_ta
  from unittest import skip, TestCase
  from pandas import DataFrame
label_desc: Use image node_id 7 for calling the TestStatisticsExtension obj's underlying member method code with example usage: obj.test_mad_ext() without return types