code: def test_to_csv_with_path_and_basic_options_multiindex_columns(self):
      pdf = pd.DataFrame(
          {("x", "a"): [1, 2, 3], ("y", "b"): ["a", "b", "c"]}
      )
      psdf = ps.DataFrame(pdf)
  
      with self.temp_dir() as dirpath:
          with self.assertRaises(ValueError):
              psdf.to_csv(
                  dirpath, num_files=1, sep="|", columns=[("x", "a")]
              )
  
          psdf.to_csv(
              dirpath,
              num_files=1,
              sep="|",
              header=["a"],
              columns=[("x", "a")],
          )
          pdf.columns = ["a", "b"]
          expected = pdf.to_csv(index=False, sep="|", columns=["a"])
  
          self._check_output(dirpath, expected)
  
imports: import os
  from contextlib import contextmanager
  import pandas
  import numpy
  from pyspark import pandas
  from pyspark.testing.pandasutils import PandasOnSparkTestCase, TestUtils
label_desc: Use image node_id 22 for calling the CsvTestsMixin obj's underlying member method code with example usage: obj.test_to_csv_with_path_and_basic_options_multiindex_columns() without return types