code: def testBleuInvalidTokenizer(self):
      invalid_tokenizer = "invalid_tokenizer_name"
      bleu_metric = bleu.Bleu(tokenize=invalid_tokenizer)
      with self.assertRaisesRegex(KeyError, invalid_tokenizer):
          bleu_metric.computations()
  
imports: from absl.testing import parameterized
  import apache_beam
  from apache_beam.testing import util
  import numpy
  import tensorflow
  import tensorflow_model_analysis
  from tensorflow_model_analysis import constants
  from tensorflow_model_analysis.eval_saved_model import testutil
  from tensorflow_model_analysis.evaluators import metrics_plots_and_validations_evaluator
  from tensorflow_model_analysis.metrics import bleu
  from tensorflow_model_analysis.metrics import metric_types
  from tensorflow_model_analysis.metrics import metric_util
  from tensorflow_model_analysis.slicer import slicer_lib
  from google.protobuf import text_format
label_desc: Use image node_id 6 for calling the BleuTest obj's underlying member method code with example usage: obj.testBleuInvalidTokenizer() without return types