code: def _opref_exists(run_dir):
      opref_path = os.path.join(run_dir, ".guild", "opref")
      return os.path.exists(opref_path)
  
imports: import errno
  import functools
  import logging
  import os
  import shutil
  import tempfile
  from guild import config
  from guild import run
  from guild import util
label_desc: Use image node_id 20 for calling a global function with example usage: _opref_exists(run_dir) and returns: os