docs: def _call(callable_obj, arg_names, namespace):
      """Actually calls the callable with the namespace parsed from the command
      line.
  
      Args:
          callable_obj: a callable object
          arg_names: name of the function arguments
          namespace: the namespace object parsed from the command line
      """
      arguments = {arg_name: getattr(namespace, arg_name)
                   for arg_name in arg_names}
      return callable_obj(**arguments)