class_docstr: Basically a list of TimeSteps with convenience methods.
class_docstr_tok: ["Basically","a","list","of","TimeSteps","with","convenience","methods","."]
code: def last_time_step(self):
      # Pre-conditions: self._time_steps shouldn't be empty.
      assert self._time_steps
      return self._time_steps[-1]
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import pickle
  import re
  import sys
  import time
  from absl import logging
  import cloudpickle
  import numpy
  from tensor2tensor.envs import time_step
  import tensorflow.compat.v1
label_desc: Use image node_id 6 for calling the Trajectory obj's underlying member method code with example usage: obj.last_time_step() and returns: self