code: def test_escape_column_name():
      index = pd.to_datetime(["2021-01-01", "2021-01-02", "2021-01-03"])
      index.name = "__timestamp"
      columns = pd.MultiIndex.from_arrays(
          [
              ["level1,value1", "level1,value2", "level1,value3"],
              ["level2, value1", "level2, value2", "level2, value3"],
          ],
          names=["level1", "level2"],
      )
      df = pd.DataFrame(index=index, columns=columns, data=1)
      assert list(pp.flatten(df).columns.values) == [
          "__timestamp",
          "level1\\,value1"
          + FLAT_COLUMN_SEPARATOR
          + "level2\\, value1",
          "level1\\,value2"
          + FLAT_COLUMN_SEPARATOR
          + "level2\\, value2",
          "level1\\,value3"
          + FLAT_COLUMN_SEPARATOR
          + "level2\\, value3",
      ]
  
file_path: superset/tests/unit_tests/pandas_postprocessing/test_flatten.py
imports: import pandas
  from superset.utils import pandas_postprocessing
  from superset.utils.pandas_postprocessing.utils import FLAT_COLUMN_SEPARATOR
  from tests.unit_tests.fixtures.dataframes import timeseries_df
label_desc: Use image node_id 8 for calling a global function with example usage: test_escape_column_name() without return types