code: def get_default_runner(udf_class, input_col_delim=',', null_indicator='NULL', stdin=None):
      
      proto = udf.get_annotation(udf_class)
      in_types, out_types = parse_proto(proto)
      stdin = stdin or sys.stdin
      arg_parser = ArgParser(in_types, stdin, input_col_delim, null_indicator)
      stdin_feed = make_feed(arg_parser)
      collector = StdoutCollector(out_types)
      ctor = _get_runner_class(udf_class)
      return ctor(udf_class, stdin_feed, collector)
docs: Create a default runner with specified udf class.