code: def test_to_csv_string_with_lf(self):
      # GH 20353
      data = {"int": [1, 2, 3], "str_lf": ["abc", "d\nef", "g\nh\n\ni"]}
      df = DataFrame(data)
      with tm.ensure_clean("lf_test.csv") as path:
          # case 1: The default line terminator(=os.linesep)(PR 21406)
          os_linesep = os.linesep.encode("utf-8")
          expected_noarg = (
              b"int,str_lf"
              + os_linesep
              + b"1,abc"
              + os_linesep
              + b'2,"d\nef"'
              + os_linesep
              + b'3,"g\nh\n\ni"'
              + os_linesep
          )
          df.to_csv(path, index=False)
          with open(path, "rb") as f:
              assert f.read() == expected_noarg
      with tm.ensure_clean("lf_test.csv") as path:
          # case 2: LF as line terminator
          expected_lf = b'int,str_lf\n1,abc\n2,"d\nef"\n3,"g\nh\n\ni"\n'
          df.to_csv(path, lineterminator="\n", index=False)
          with open(path, "rb") as f:
              assert f.read() == expected_lf
      with tm.ensure_clean("lf_test.csv") as path:
          # case 3: CRLF as line terminator
          # 'lineterminator' should not change inner element
          expected_crlf = (
              b'int,str_lf\r\n1,abc\r\n2,"d\nef"\r\n3,"g\nh\n\ni"\r\n'
          )
          df.to_csv(path, lineterminator="\r\n", index=False)
          with open(path, "rb") as f:
              assert f.read() == expected_crlf
  
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 20 for calling the TestToCSV obj's underlying member method code with example usage: obj.test_to_csv_string_with_lf() without return types