def normalize_partial_args(partial_specs):
  """Normalize the shorthand form of a partial's args specification.

  Turns this:

    partial:
      args:
        SOME_ARG: arg_value

  Into this:

    partial:
       args:
         SOME_ARG:
            default: arg_value

  Args:
    partial_specs: The dict from spec.yml["partials"]. This dict is modified in
      place.

  Returns:
    The modified contents of partial_specs.

  """
  for _, partial in partial_specs.items():
    args = partial.get('args', dict())
    for arg, value in args.items():
      if not isinstance(value, dict):
        new_value = {'default': value}
        args[arg] = new_value

  return partial_specs