code: def extract_trailing_metadata(
      error: grpc.aio.AioRpcError,
  ) -> Optional[str]:
      """Return formatted string of the trailing metadata if exists otherwise return None
      :param error: AioRpcError
      :return: string of Metadata or None
      """
      if type(error) == grpc.aio.AioRpcError:
          trailing_metadata = error.trailing_metadata()
          if trailing_metadata and len(trailing_metadata):
              return f"trailing_metadata={trailing_metadata}"
  
      return None
  
file_path: jina/jina/serve/helper.py
imports: import functools
  import inspect
  import os
  import typing
  from typing import Any, Dict, List, Optional, Tuple, Union
  import grpc
  from jina.helper import convert_tuple_to_list
  from contextlib import nullcontext
label_desc: Use image node_id 4 for calling a global function with example usage: extract_trailing_metadata(error) and returns: None, str, trailing_metadata