class_docstr: Manages interactions between agents on messenger as well as direct interactions
  between agents and the messenger overworld.
code: def _confirm_message_delivery(self, event):
      # By default we don't actually do anything when messages are marked as
      # being delivered, but we expose the ability for others to
      self._log_debug(
          "Messages {} marked as received.".format(
              event["delivery"]["mids"]
          )
      )
  
imports: import logging
  import os
  from parlai.core.agents import create_agent
  import parlai.chat_service.utils.logging
  import parlai.chat_service.utils.server
  from parlai.utils.io import PathManager
  from parlai.chat_service.services.messenger.agents import MessengerAgent
  from parlai.chat_service.core.socket import ChatServiceMessageSocket
  from parlai.chat_service.services.messenger.message_sender import MessageSender
  from parlai.chat_service.core.chat_service_manager import ChatServiceManager
label_desc: Use image node_id 9 for calling the MessengerManager obj's underlying member method code with example usage: obj._confirm_message_delivery(event) without return types