code: def test_concat_multiindex_(self):
      # GitHub #44786
      df = DataFrame({"col": ["a", "b", "c"]}, index=["1", "2", "2"])
      df = concat([df], keys=["X"])
  
      iterables = [["X"], ["1", "2", "2"]]
      result_index = df.index
      expected_index = MultiIndex.from_product(iterables)
  
      tm.assert_index_equal(result_index, expected_index)
  
      result_df = df
      expected_df = DataFrame(
          {"col": ["a", "b", "c"]},
          index=MultiIndex.from_product(iterables),
      )
      tm.assert_frame_equal(result_df, expected_df)
  
imports: from copy import deepcopy
  import numpy
  import pytest
  from pandas.errors import PerformanceWarning
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series, concat
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestMultiIndexConcat obj's underlying member method code with example usage: obj.test_concat_multiindex_() without return types