code: def _zero_pad(sequence_length: int) -> datasets.Transform:
      """Adds zero padding to the right so all samples have the same length."""
  
      def _zero_pad_transform(
          sample: reverb.ReplaySample,
      ) -> reverb.ReplaySample:
          trajectory: reverb_base.Trajectory = sample.data
  
          # Split steps and extras data (the extras won't be padded as they only
          # contain one element)
          trajectory_steps = trajectory._asdict()
          trajectory_extras = trajectory_steps.pop("extras")
  
          unpadded_length = len(tree.flatten(trajectory_steps)[0])
  
          # Do nothing if the sequence is already full.
          if unpadded_length != sequence_length:
              to_pad = sequence_length - unpadded_length
              pad = lambda x: tf.pad(
                  x, [[0, to_pad]] + [[0, 0]] * (len(x.shape) - 1)
              )
  
              trajectory_steps = tree.map_structure(
                  pad, trajectory_steps
              )
  
          # Set the shape to be statically known, and checks it at runtime.
          def _ensure_shape(x):
              shape = tf.TensorShape([sequence_length]).concatenate(
                  x.shape[1:]
              )
              return tf.ensure_shape(x, shape)
  
          trajectory_steps = tree.map_structure(
              _ensure_shape, trajectory_steps
          )
          return reverb.ReplaySample(
              info=sample.info,
              data=reverb_base.Trajectory(
                  **trajectory_steps, extras=trajectory_extras
              ),
          )
  
      return _zero_pad_transform
  
imports: from typing import Generic, Iterator, List, Optional
  import acme
  from acme import adders
  from acme import core
  from acme import specs
  from acme.adders import reverb
  from acme.adders.reverb import base
  from acme.adders.reverb import structured
  from acme.agents.jax import actor_core
  from acme.agents.jax import actors
  from acme.agents.jax import builders
  from acme.agents.jax.r2d2 import actor
  from acme.agents.jax.r2d2 import config
  from acme.agents.jax.r2d2 import learning
  from acme.agents.jax.r2d2 import networks
  from acme.datasets import reverb
  from acme.jax import networks
  from acme.jax import utils
  from acme.jax import variable_utils
  from acme.utils import counting
  from acme.utils import loggers
  import jax
  import optax
  import reverb
  from reverb import structured_writer
  import tensorflow
  import tree
label_desc: Use image node_id 2 for calling a global function with example usage: _zero_pad(sequence_length) and returns: _zero_pad_transform, reverb, tf