code: def test_subclass_unstack(self):
      # GH 15564
      df = tm.SubclassedDataFrame(
          [[1, 2, 3], [4, 5, 6], [7, 8, 9]],
          index=["a", "b", "c"],
          columns=["X", "Y", "Z"],
      )
  
      res = df.unstack()
      exp = tm.SubclassedSeries(
          [1, 4, 7, 2, 5, 8, 3, 6, 9],
          index=[list("XXXYYYZZZ"), list("abcabcabc")],
      )
  
      tm.assert_series_equal(res, exp)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 11 for calling the TestDataFrameSubclassing obj's underlying member method code with example usage: obj.test_subclass_unstack() without return types