code: def test_write_to_io():
      doc = CoNLL.conll2doc(input_str=ENGLISH_SAMPLE)
      output = io.StringIO()
      CoNLL.write_doc2conll(doc, output)
      output_value = output.getvalue()
      assert output_value.endswith("\n\n")
      assert output_value.strip() == ENGLISH_SAMPLE
  
imports: import io
  import pytest
  import tempfile
  from zipfile import ZipFile
  import stanza
  from stanza.utils.conll import CoNLL
  from stanza.models.common.doc import Document
  from stanza.tests import *
label_desc: Use image node_id 6 for calling a global function with example usage: test_write_to_io() without return types