code: def _process_value_fetcher_call_args(args):
      
      if not args:
          return _undefined, ()
  
      if isinstance(args[0], JSONValueMapper):
          default = _undefined
          mappers = args
      else:
          default = args[0]
          mappers = args[1:]
  
      for mapper in mappers:
          if not isinstance(mapper, JSONValueMapper):
              raise TypeError('%r isn\'t a JSONValueMapper instance!' % (mapper,))
  
      return default, mappers
docs: This function processes the incoming varargs of ValueNotFoundNode.__call__() and
      _ConfigNode.__call__().
      :param args: A list or tuple containing positional function call arguments. The optional
      arguments we expect are the following: An optional default value followed by zero or more
      JSONValueMapper instances.
      :return: (default_value, list_or_tuple_of_JSONValueMapper_instances)
      The default_value is _undefined if it is not present and the second item of the tuple is
      an empty tuple/list if there are not JSONValueMapper instances.