docstr: Test saving and re-initialization.
code: def test_task_save_init(self):
      """Test saving and re-initialization."""
      task1 = rl_task.RLTask(
          DummyEnv(), initial_trajectories=13, max_steps=9, gamma=0.9
      )
      self.assertLen(task1.trajectories[0], 13)
      self.assertEqual(task1.max_steps, 9)
      self.assertEqual(task1.gamma, 0.9)
      temp_file = os.path.join(
          self.create_tempdir().full_path, "task.pkl"
      )
      task1.save_to_file(temp_file)
      task2 = rl_task.RLTask(
          DummyEnv(), initial_trajectories=3, max_steps=19, gamma=1.0
      )
      self.assertLen(task2.trajectories[0], 3)
      self.assertEqual(task2.max_steps, 19)
      self.assertEqual(task2.gamma, 1.0)
      task2.init_from_file(temp_file)
      self.assertLen(task2.trajectories[0], 13)
      self.assertEqual(task2.max_steps, 9)
      self.assertEqual(task2.gamma, 0.9)
  
imports: import os
  from absl.testing import absltest
  import gym
  import numpy
  from trax import test_utils
  from trax.rl import task
label_desc: Use image node_id 19 for calling the TaskTest obj's underlying member method code with example usage: obj.test_task_save_init() without return types