code: def test_creation(self):
      bt = trajectory.BatchTrajectory(batch_size=self.BATCH_SIZE)
  
      self.assertEqual(self.BATCH_SIZE, len(bt.trajectories))
      self.assertEqual(0, bt.num_completed_trajectories)
  
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 2 for calling the BatchTrajectoryTest obj's underlying member method code with example usage: obj.test_creation() without return types