docstr: Toy example where Input='1 2', Output='2', References=['1 2', 1'].
docstr_tok: ["Toy","example","where","Input=","'","1","2","'",",","Output=","'","2","'",",","References=","[","'","1","2","'",",","1","'","]","."]
code: def testKeepScore(self):
      """Toy example where Input='1 2', Output='2', References=['1 2', 1']."""
      # Unigram counts.
      source_counts = collections.Counter({1: 1, 2: 1})
      prediction_counts = collections.Counter({2: 1})
      target_counts = collections.Counter({1: 1, 2: 0.5})
      score = sari_hook.get_keep_score(
          source_counts, prediction_counts, target_counts
      )
      self.assertAlmostEqual(6.0 / 15, score)
  
file_path: tensor2tensor/tensor2tensor/utils/sari_hook_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import numpy
  from tensor2tensor.utils import sari_hook
  import tensorflow.compat.v1
label_desc: Use image node_id 8 for calling the SariHookTest obj's underlying member method code with example usage: obj.testKeepScore() without return types