code: def test_cooccurrence_vectorizer_should_persist(self):
      # Given
      x = [text_to_utterance("yoo yoo")]
      dataset = get_empty_dataset("en")
      shared = self.get_shared_data(dataset)
      vectorizer = CooccurrenceVectorizer(**shared).fit(x, dataset)
      vectorizer.builtin_entity_scope = {"snips/entity"}
  
      # When
      vectorizer.persist(self.tmp_file_path)
  
      # Then
      metadata_path = self.tmp_file_path / "metadata.json"
      expected_metadata = {"unit_name": "cooccurrence_vectorizer"}
      self.assertJsonContent(metadata_path, expected_metadata)
  
      vectorizer_path = self.tmp_file_path / "vectorizer.json"
      expected_vectorizer = {
          "word_pairs": {"0": ["yoo", "yoo"]},
          "language_code": "en",
          "config": vectorizer.config.to_dict(),
          "builtin_entity_scope": ["snips/entity"],
      }
      self.assertJsonContent(vectorizer_path, expected_vectorizer)
  
imports: from __future__ import unicode_literals
  import io
  from builtins import str, zip, range
  import numpy
  from checksumdir import dirhash
  from mock import patch, MagicMock
  from snips_nlu.common.io_utils import temp_dir
  from snips_nlu.common.utils import json_string
  from snips_nlu.constants import LANGUAGE_EN, STEMS, WORD_CLUSTERS, STOP_WORDS
  from snips_nlu.dataset import Dataset
  from snips_nlu.entity_parser import BuiltinEntityParser, CustomEntityParser
  from snips_nlu.entity_parser.custom_entity_parser_usage import CustomEntityParserUsage
  from snips_nlu.exceptions import _EmptyDatasetUtterancesError
  from snips_nlu.intent_classifier.featurizer import CooccurrenceVectorizer, Featurizer, TfidfVectorizer
  from snips_nlu.intent_classifier.log_reg_classifier_utils import text_to_utterance
  from snips_nlu.pipeline.configs import FeaturizerConfig
  from snips_nlu.pipeline.configs.intent_classifier import CooccurrenceVectorizerConfig, TfidfVectorizerConfig
  from snips_nlu.tests.utils import FixtureTest, get_empty_dataset, EntityParserMock
label_desc: Use image node_id 1 for calling the CooccurrenceVectorizerTest obj's underlying member method code with example usage: obj.test_cooccurrence_vectorizer_should_persist() without return types