code: def test_multindex_columns_pairwise_func(self):
      # GH 21157
      columns = MultiIndex.from_arrays(
          [["M", "N"], ["P", "Q"]], names=["a", "b"]
      )
      df = DataFrame(np.ones((5, 2)), columns=columns)
      result = df.rolling(3).corr()
      expected = DataFrame(
          np.nan,
          index=MultiIndex.from_arrays(
              [
                  np.repeat(np.arange(5, dtype=np.int64), 2),
                  ["M", "N"] * 5,
                  ["P", "Q"] * 5,
              ],
              names=[None, "a", "b"],
          ),
          columns=columns,
      )
      tm.assert_frame_equal(result, expected)
  
imports: import numpy
  import pytest
  from pandas.compat import IS64
  from pandas import DataFrame, Index, MultiIndex, Series, date_range
  import pandas._testing
  from pandas.core.algorithms import safe_sort
label_desc: Use image node_id 9 for calling the TestPairwise obj's underlying member method code with example usage: obj.test_multindex_columns_pairwise_func() without return types