docstr: Test the extraction of labels from a dataset
docstr_tok: ["Test","the","extraction","of","labels","from","a","dataset"]
code: def test_dataset_labels(self, train_file):
      """
      Test the extraction of labels from a dataset
      """
      train_set = data.read_dataset(str(train_file), WVType.OTHER, 1)
      labels = data.dataset_labels(train_set)
      assert labels == ["0", "1", "2"]
  
file_path: stanza/stanza/tests/classifiers/test_data.py
imports: import json
  import pytest
  import stanza.models.classifiers.data
  from stanza.models.classifiers.utils import WVType
  from stanza.models.common.vocab import PAD, UNK
  from stanza.models.constituency.parse_tree import Tree
label_desc: Use image node_id 4 for calling the TestClassifierData obj's underlying member method code with example usage: obj.test_dataset_labels(train_file) without return types