code: def timer(start_time=None):
      if not start_time:
          return time.time()
      return time.time() - start_time
  
imports: import os
  import time
  import jax
  import optax
  import threading
  import numpy
  import logging
  from queue import Queue, Empty
  from jax.experimental import maps
  from transformers import GPT2TokenizerFast
  from mesh_transformer.checkpoint import read_ckpt
  from mesh_transformer.sampling import nucleaus_sample
  from mesh_transformer.transformer_shard import CausalTransformer
label_desc: Use image node_id 3 for calling a global function with example usage: timer(start_time) and returns: unknown, time