code: def opt_str(x):
      if x is None:
          return x
      return str(x)
  
imports: import asyncio
  import inspect
  import os
  import re
  import textwrap
  import warnings
  from shlex import quote
  from typing import Any, Callable, Dict, List, Optional, Set, Tuple, Union, cast, Literal
  from typing_extensions import Self
  import hailtop.batch_client.client
  from .None import backend, batch
  from .None import resource
  from .exceptions import BatchException
label_desc: Use image node_id 2 for calling a global function with example usage: opt_str(x) and returns: str, x