code: def save_checkpoint(path, state, keep=2):
      """Save the state to a checkpoint."""
      state_to_save = jax.device_get(
          jax.tree_map(lambda x: x[0], state)
      )
      step = state_to_save.optimizer.state.step
      checkpoint_path = checkpoints.save_checkpoint(
          path, state_to_save, step, keep=keep
      )
      logging.info(
          "Saved checkpoint: step=%d, path=%s",
          int(step),
          checkpoint_path,
      )
      return checkpoint_path
  
imports: import functools
  from typing import Any
  from typing import Callable
  from typing import Dict
  from absl import logging
  from flax import struct
  from flax.training import checkpoints
  import jax
  from jax import lax
  from jax import numpy
  from jax import random
  from jax import vmap
  from nerfies import model_utils
  from nerfies import models
  from nerfies import utils
label_desc: Use image node_id 1 for calling a global function with example usage: save_checkpoint(path, state, keep) and returns: checkpoint_path