code: def make_sequence(observations):
      """Create a sequence of timesteps of the form `first, [second, ..., last]`."""
      first, steps = make_trajectory(observations)
      observation = first.observation
      sequence = []
      start_of_episode = True
      for action, timestep in steps:
          extras = ()
          sequence.append(
              (
                  observation,
                  action,
                  timestep.reward,
                  timestep.discount,
                  start_of_episode,
                  extras,
              )
          )
          observation = timestep.observation
          start_of_episode = False
      sequence.append((observation, 0, 0.0, 0.0, False, ()))
      return sequence
  
imports: from typing import Any, Callable, Optional, Sequence, Tuple, TypeVar, Union
  from acme import specs
  from acme import types
  from acme.adders import base
  from acme.adders import reverb
  from acme.utils import tree_utils
  import dm_env
  import numpy
  import reverb
  import tensorflow
  import tree
  from absl.testing import absltest
label_desc: Use image node_id 2 for calling a global function with example usage: make_sequence(observations) and returns: sequence