code: def test_log_best_features(self):
      # Given
      dataset_stream = io.StringIO(
          """
  ---
  type: intent
  name: intent1
  utterances:
    - foo bar
  
  ---
  type: intent
  name: intent2
  utterances:
    - lorem ipsum"""
      )
      dataset = Dataset.from_yaml_files("en", [dataset_stream]).json
      shared = self.get_shared_data(dataset)
      intent_classifier = LogRegIntentClassifier(**shared)
  
      # When
      self.assertIsNone(intent_classifier.log_best_features(20))
      intent_classifier.fit(dataset)
      log = intent_classifier.log_best_features(20)
  
      # Then
      self.assertIsInstance(log, str)
      self.assertIn("Top 20", log)
  
imports: from __future__ import unicode_literals
  import io
  import sys
  from builtins import str
  from unittest import skipIf
  from checksumdir import dirhash
  from mock import patch
  from snips_nlu.common.io_utils import temp_dir
  from snips_nlu.constants import INTENTS, LANGUAGE_EN, RES_INTENT_NAME, RES_PROBA, UTTERANCES
  from snips_nlu.dataset import Dataset
  from snips_nlu.exceptions import NotTrained
  from snips_nlu.intent_classifier import LogRegIntentClassifier
  from snips_nlu.intent_classifier.featurizer import Featurizer
  from snips_nlu.intent_classifier.log_reg_classifier_utils import text_to_utterance
  from snips_nlu.pipeline.configs import LogRegIntentClassifierConfig
  from snips_nlu.result import intent_classification_result
  from snips_nlu.tests.utils import FixtureTest, get_empty_dataset
label_desc: Use image node_id 15 for calling the TestLogRegIntentClassifier obj's underlying member method code with example usage: obj.test_log_best_features() without return types