code: def get_active_config_file():
      f = LOCAL_CONFIG_FILE_OVERRIDE_VAR.get()
      if f and exists(expanduser(expandvars(f))):
          return f
      for f in LOCAL_CONFIG_FILES:
          if exists(expanduser(expandvars(f))):
              return f
      return None
  
file_path: clearml/clearml/backend_config/defs.py
imports: from os.path import expanduser, expandvars, exists
  from pathlib2 import Path
  from .environment import EnvEntry
label_desc: Use image node_id 2 for calling a global function with example usage: get_active_config_file() and returns: None, f, f