code: def testRestartIsFirst(self):
      observation = tf.constant(-1)
      time_step = ts.restart(observation)
      is_first = time_step.is_first()
      self.assertEqual(True, self.evaluate(is_first))
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import sys
  import numpy
  import tensorflow
  from tf_agents.specs import array_spec
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import time_step
  from tf_agents.utils import nest_utils
label_desc: Use image node_id 8 for calling the TFTimeStepTest obj's underlying member method code with example usage: obj.testRestartIsFirst() without return types