code: def test_empty_trajectory(self):
      t = trajectory.Trajectory()
      self.assertFalse(t.is_active)
      self.assertEqual(0, t.num_time_steps)
      self.assertFalse(t.done)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import numpy
  from tensor2tensor.envs import time_step
  from tensor2tensor.envs import trajectory
  import tensorflow.compat.v1
  from tensorflow.compat.v1.io import gfile
label_desc: Use image node_id 1 for calling the TrajectoryTest obj's underlying member method code with example usage: obj.test_empty_trajectory() without return types