code: def test___init__(self):
      corpus = PlainTextCorpus()
      self.assertIsNone(corpus.documents)
  
file_path: underthesea/tests/corpus/test_plaintext.py
imports: import os
  import shutil
  from os import listdir
  from unittest import TestCase
  from os.path import join
  import sys
  from underthesea.corpus import PlainTextCorpus
label_desc: Use image node_id 2 for calling the TestPlainTextCorpus obj's underlying member method code with example usage: obj.test___init__() without return types