code: def message_with_placeholders(message):
      
      new_message = message.copy()
      for attr in PLACEHOLDER_FORMAT.keys():
          if message.get(attr) is not None:
              content = message[attr]
              placeholder = PLACEHOLDER_FORMAT[attr].format(length=len(content))
              new_message[attr] = placeholder
      return new_message
docs: Return an ASGI message, with any body-type content omitted and replaced
      with a placeholder.