code: def test_reuses_sessions(self):
      self._square(123)
      self.assertEqual(tf.Session.call_count, 1)
      self._square(234)
      self.assertEqual(tf.Session.call_count, 1)
  
file_path: tensorboard/tensorboard/util/op_evaluator_test.py
imports: import tensorflow.compat.v1
  from tensorboard.util import op_evaluator
label_desc: Use image node_id 4 for calling the PersistentOpEvaluatorTest obj's underlying member method code with example usage: obj.test_reuses_sessions() without return types