code: def fill_missing_args(args, add_arguments):
      """Fill missing arguments in args.
  
      Args:
          args (Namespace or None): Namesapce containing hyperparameters.
          add_arguments (function): Function to add arguments.
  
      Returns:
          Namespace: Arguments whose missing ones are filled with default value.
  
      Examples:
          >>> from argparse import Namespace
          >>> from espnet.nets.pytorch_backend.e2e_tts_tacotron2 import Tacotron2
          >>> args = Namespace()
          >>> fill_missing_args(args, Tacotron2.add_arguments_fn)
          Namespace(aconv_chans=32, aconv_filts=15, adim=512, atype='location', ...)
  
      """
      # check argument type
      assert isinstance(args, argparse.Namespace) or args is None
      assert callable(add_arguments)
  
      # get default arguments
      default_args, _ = add_arguments(
          argparse.ArgumentParser()
      ).parse_known_args()
  
      # convert to dict
      args = {} if args is None else vars(args)
      default_args = vars(default_args)
  
      for key, value in default_args.items():
          if key not in args:
              logging.info(
                  'attribute "%s" does not exist. use default %s.'
                  % (key, str(value))
              )
              args[key] = value
  
      return argparse.Namespace(**args)
  
label_desc: Use image node_id 1 for calling a global function with example usage: fill_missing_args(args, add_arguments) and returns: argparse