code: def test_sents(self):
      first_3_sents = sinica_treebank.sents()[:3]
      self.assertEqual(
          first_3_sents,
          [["一"], ["友情"], ["嘉珍", "和", "我", "住在", "同一條", "巷子"]],
      )
  
imports: import unittest
  import pytest
  from nltk.corpus import cess_cat, cess_esp, conll2007, floresta, indian, ptb, sinica_treebank, udhr
  from nltk.tree import Tree
label_desc: Use image node_id 1 for calling the TestSinicaTreebank obj's underlying member method code with example usage: obj.test_sents() without return types