code: def test_to_csv_na_rep_nullable_string(self, nullable_string_dtype):
      # GH 29975
      # Make sure full na_rep shows up when a dtype is provided
      expected = tm.convert_rows_list_to_csv_str(
          [",0", "0,a", "1,ZZZZZ", "2,c"]
      )
      csv = pd.Series(
          ["a", pd.NA, "c"], dtype=nullable_string_dtype
      ).to_csv(na_rep="ZZZZZ")
      assert expected == csv
  
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 10 for calling the TestToCSV obj's underlying member method code with example usage: obj.test_to_csv_na_rep_nullable_string(nullable_string_dtype) without return types