code: def test_to_csv_no_index(self):
      # GH 3624, after appending columns, to_csv fails
      with tm.ensure_clean("__tmp_to_csv_no_index__") as path:
          df = DataFrame({"c1": [1, 2, 3], "c2": [4, 5, 6]})
          df.to_csv(path, index=False)
          result = read_csv(path)
          tm.assert_frame_equal(df, result)
          df["c3"] = Series([7, 8, 9], dtype="int64")
          df.to_csv(path, index=False)
          result = read_csv(path)
          tm.assert_frame_equal(df, result)
  
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 20 for calling the TestDataFrameToCSV obj's underlying member method code with example usage: obj.test_to_csv_no_index() without return types