docstr: Insert `num_step` random observations into Reverb server.
code: def _insert_random_data(
      self, env, num_steps, sequence_length=2, additional_observers=None
  ):
      """Insert `num_step` random observations into Reverb server."""
      observers = (
          [] if additional_observers is None else additional_observers
      )
      traj_obs = reverb_utils.ReverbAddTrajectoryObserver(
          self._py_client,
          self._table_name,
          sequence_length=sequence_length,
      )
      observers.append(traj_obs)
      policy = random_py_policy.RandomPyPolicy(
          env.time_step_spec(), env.action_spec()
      )
      driver = py_driver.PyDriver(
          env, policy, observers=observers, max_steps=num_steps
      )
      time_step = env.reset()
      driver.run(time_step)
      traj_obs.close()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import reverb
  import tensorflow
  from tf_agents.drivers import py_driver
  from tf_agents.environments import test_envs
  from tf_agents.policies import random_py_policy
  from tf_agents.replay_buffers import reverb_replay_buffer
  from tf_agents.replay_buffers import reverb_utils
  from tf_agents.specs import array_spec
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import trajectory
  from tf_agents.utils import common
  from tf_agents.utils import test_utils
label_desc: Use image node_id 3 for calling the ReverbReplayBufferTest obj's underlying member method code with example usage: obj._insert_random_data(env, num_steps, sequence_length, additional_observers) without return types