code: def test_read_data_source(self):
      data = list(self.data.train)
      self.assertEqual(10, len(data))
      example = next(iter(data))
      self.assertEqual(2, len(example))
      self.assertEqual({"label", "text"}, set(example))
  
imports: import unittest
  from typing import List
  from pytext.data.sources.data_source import SafeFileWrapper
  from pytext.data.sources.tsv import BlockShardedTSVDataSource, SessionTSVDataSource, TSVDataSource
  from pytext.utils.test import import_tests_module
label_desc: Use image node_id 2 for calling the TSVDataSourceTest obj's underlying member method code with example usage: obj.test_read_data_source() without return types