code: def test_nl_generator_empty_input(self):
      generator = nlsg.NLStatsGenerator(None, None, 0, 0, 0)
      self.assertCombinerOutputEqual(
          [], generator, self._create_expected_feature_name_statistics()
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import tempfile
  from absl.testing import absltest
  import pyarrow
  from tensorflow_data_validation import types
  from tensorflow_data_validation.statistics.generators import natural_language_stats_generator
  from tensorflow_data_validation.utils import test_util
  from google.protobuf import text_format
  from tensorflow_metadata.proto.v0 import schema_pb2
  from tensorflow_metadata.proto.v0 import statistics_pb2
label_desc: Use image node_id 4 for calling the NaturalLanguageStatsGeneratorTest obj's underlying member method code with example usage: obj.test_nl_generator_empty_input() without return types