code: def start_background(self):
      with self.lock:
          t = threading.Thread(target=self.background)
          t.start()
  
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 the GPTJ obj's underlying member method code with example usage: obj.start_background() without return types