code: def test_get_learning_rate(self):
      optimizer = tf.compat.v1.train.AdamOptimizer(learning_rate=0.1)
      learning_rate = ppo_utils.get_learning_rate(optimizer)
      expected_learning_rate = 0.1
      self.assertAlmostEqual(expected_learning_rate, learning_rate)
  
file_path: agents/tf_agents/agents/ppo/ppo_utils_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import tensorflow
  import tensorflow_probability
  from tf_agents.agents.ppo import ppo_utils
  from tf_agents.trajectories import time_step
label_desc: Use image node_id 4 for calling the PPOUtilsTest obj's underlying member method code with example usage: obj.test_get_learning_rate() without return types