code: def test_len_unicode(self):
      ds = self._dataset(["utf8_1.txt"], encoding="utf-8")
      assert len(ds) == 3
  
imports: from __future__ import unicode_literals
  import os
  import pickle
  import unittest
  import six
  from chainer import datasets
  from chainer import testing
label_desc: Use image node_id 7 for calling the TestTextDataset obj's underlying member method code with example usage: obj.test_len_unicode() without return types