code: def test_clean_names_preserve_case_true(multiindex_dataframe):
      """Tests clean_names `case_type` parameter = preserve."""
      df = multiindex_dataframe.clean_names(case_type="preserve")
  
      levels = [
          ["a", "Bell_Chart", "decorated_elephant"],
          ["b", "Normal_Distribution", "r_i_p_rhino"],
      ]
  
      codes = [[1, 0, 2], [1, 0, 2]]
  
      expected_columns = pd.MultiIndex(levels=levels, codes=codes)
      assert set(df.columns) == set(expected_columns)
  
file_path: pyjanitor/tests/functions/test_clean_names.py
imports: import pandas
  import pytest
  from janitor.errors import JanitorError
label_desc: Use image node_id 9 for calling a global function with example usage: test_clean_names_preserve_case_true(multiindex_dataframe) without return types