code: def test_to_csv_dtnat(self):
      # GH3437
      def make_dtnat_arr(n, nnat=None):
          if nnat is None:
              nnat = int(n * 0.1)  # 10%
          s = list(date_range("2000", freq="5min", periods=n))
          if nnat:
              for i in np.random.default_rng(2).integers(
                  0, len(s), nnat
              ):
                  s[i] = NaT
              i = np.random.default_rng(2).integers(100)
              s[-i] = NaT
              s[i] = NaT
          return s
  
      chunksize = 1000
      s1 = make_dtnat_arr(chunksize + 5)
      s2 = make_dtnat_arr(chunksize + 5, 0)
  
      with tm.ensure_clean("1.csv") as pth:
          df = DataFrame({"a": s1, "b": s2})
          df.to_csv(pth, chunksize=chunksize)
  
          recons = self.read_csv(pth).apply(to_datetime)
          tm.assert_frame_equal(df, recons, check_names=False)
  
imports: import csv
  from io import StringIO
  import os
  import numpy
  import pytest
  from pandas.errors import ParserError
  import pandas
  from pandas import DataFrame, Index, MultiIndex, NaT, Series, Timestamp, date_range, period_range, read_csv, to_datetime
  import pandas._testing
  import pandas.core.common
  from pandas.io.common import get_handle
label_desc: Use image node_id 9 for calling the TestDataFrameToCSV obj's underlying member method code with example usage: obj.test_to_csv_dtnat() and returns: s