code: def testSingleStepTensors(self):
      observation = ()
      action = ()
      policy_info = ()
      reward = tf.constant([1.0, 1.0, 2.0])
      discount = tf.constant([1.0, 1.0, 1.0])
      traj = trajectory.single_step(
          observation, action, policy_info, reward, discount
      )
      self.assertTrue(tf.is_tensor(traj.step_type))
      traj_val = self.evaluate(traj)
      self.assertAllEqual(traj_val.step_type, [ts.StepType.FIRST] * 3)
      self.assertAllEqual(
          traj_val.next_step_type, [ts.StepType.LAST] * 3
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import sys
  import numpy
  import tensorflow
  from tf_agents.drivers import dynamic_episode_driver
  from tf_agents.drivers import test_utils
  from tf_agents.environments import tf_py_environment
  from tf_agents.trajectories import time_step
  from tf_agents.trajectories import trajectory
  from tf_agents.utils import test_utils
label_desc: Use image node_id 7 for calling the TrajectoryTest obj's underlying member method code with example usage: obj.testSingleStepTensors() without return types