code: def testMetricPrefix(self):
      batched_avg_return_metric = batched_py_metric.BatchedPyMetric(
          py_metrics.AverageReturnMetric, prefix="CustomPrefix"
      )
      self.assertEqual(batched_avg_return_metric.prefix, "CustomPrefix")
  
      tf_avg_return_metric = tf_py_metric.TFPyMetric(
          batched_avg_return_metric
      )
      self.assertEqual(tf_avg_return_metric._prefix, "CustomPrefix")
  
file_path: agents/tf_agents/metrics/tf_py_metric_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import tensorflow
  from tf_agents.metrics import batched_py_metric
  from tf_agents.metrics import py_metrics
  from tf_agents.metrics import tf_py_metric
  from tf_agents.trajectories import trajectory
  from tf_agents.utils import nest_utils
label_desc: Use image node_id 3 for calling the BatchedPyMetricTest obj's underlying member method code with example usage: obj.testMetricPrefix() without return types