code: def test_subclass_stack_multi(self):
      # GH 15564
      df = tm.SubclassedDataFrame(
          [
              [10, 11, 12, 13],
              [20, 21, 22, 23],
              [30, 31, 32, 33],
              [40, 41, 42, 43],
          ],
          index=MultiIndex.from_tuples(
              list(zip(list("AABB"), list("cdcd"))),
              names=["aaa", "ccc"],
          ),
          columns=MultiIndex.from_tuples(
              list(zip(list("WWXX"), list("yzyz"))),
              names=["www", "yyy"],
          ),
      )
  
      exp = tm.SubclassedDataFrame(
          [
              [10, 12],
              [11, 13],
              [20, 22],
              [21, 23],
              [30, 32],
              [31, 33],
              [40, 42],
              [41, 43],
          ],
          index=MultiIndex.from_tuples(
              list(
                  zip(
                      list("AAAABBBB"),
                      list("ccddccdd"),
                      list("yzyzyzyz"),
                  )
              ),
              names=["aaa", "ccc", "yyy"],
          ),
          columns=Index(["W", "X"], name="www"),
      )
  
      res = df.stack(future_stack=True)
      tm.assert_frame_equal(res, exp)
  
      res = df.stack("yyy", future_stack=True)
      tm.assert_frame_equal(res, exp)
  
      exp = tm.SubclassedDataFrame(
          [
              [10, 11],
              [12, 13],
              [20, 21],
              [22, 23],
              [30, 31],
              [32, 33],
              [40, 41],
              [42, 43],
          ],
          index=MultiIndex.from_tuples(
              list(
                  zip(
                      list("AAAABBBB"),
                      list("ccddccdd"),
                      list("WXWXWXWX"),
                  )
              ),
              names=["aaa", "ccc", "www"],
          ),
          columns=Index(["y", "z"], name="yyy"),
      )
  
      res = df.stack("www", future_stack=True)
      tm.assert_frame_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 9 for calling the TestDataFrameSubclassing obj's underlying member method code with example usage: obj.test_subclass_stack_multi() without return types