code: def _check_got(self, got, expected_key):
      self.assertLen(got, 1)
      got_slice_key, got_metrics = got[0]
      self.assertEqual(got_slice_key, ())
      self.assertIn(expected_key, got_metrics)
      return got_metrics
  
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 1 for calling the BleuTest obj's underlying member method code with example usage: obj._check_got(got, expected_key) and returns: got_metrics