code: def test_different(self):
      ref = "this is a string"
      inputs = [{"answers": [ref, ref]}, {"answers": [ref, ref]}]
  
      with mock.patch.object(
          seqio.test_utils.MockVocabulary, "decode", new=mock_decode
      ):
          vocabulary = seqio.test_utils.MockVocabulary(
              {"this": 2, "is": 3, "a": 4, "string": 5, "": 6},
              vocab_size=10,
          )
  
          model_output = np.array([[6], [6]])
          features = {"targets": seqio.Feature(vocabulary)}
          metric = metrics.ShardedSquad.from_model_output(
              inputs, model_output, features
          )
          self.assertDictClose(metric.compute(), {"em": 0, "f1": 0})
  
imports: from unittest import mock
  from absl.testing import absltest
  import numpy
  import seqio
  import sklearn.metrics
  from t5.evaluation import metrics
  from t5.evaluation import test_utils
label_desc: Use image node_id 2 for calling the ShardedSquadTest obj's underlying member method code with example usage: obj.test_different() without return types