code: def test_to_csv_different_datetime_formats(self):
      # GH#21734
      df = DataFrame(
          {
              "date": pd.to_datetime("1970-01-01"),
              "datetime": pd.date_range(
                  "1970-01-01", periods=2, freq="h"
              ),
          }
      )
      expected_rows = [
          "date,datetime",
          "1970-01-01,1970-01-01 00:00:00",
          "1970-01-01,1970-01-01 01:00:00",
      ]
      expected = tm.convert_rows_list_to_csv_str(expected_rows)
      assert df.to_csv(index=False) == expected
  
imports: import io
  import os
  import sys
  from zipfile import ZipFile
  from _csv import Error
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, compat
  import pandas._testing
label_desc: Use image node_id 12 for calling the TestToCSV obj's underlying member method code with example usage: obj.test_to_csv_different_datetime_formats() without return types