code: def post_message(self, message) -> DBHandlerResponse:
      try:
          response = self.client.chat_postMessage(
              channel=self.channel, text=message
          )
          return DBHandlerResponse(data=response["message"]["text"])
      except SlackApiError as e:
          assert e.response["ok"] is False
          assert e.response["error"]
          return DBHandlerResponse(data=None, error=e.response["error"])
  
file_path: evadb/evadb/third_party/databases/slack/slack_handler.py
imports: import pandas
  from slack_sdk import WebClient
  from slack_sdk.errors import SlackApiError
  from evadb.third_party.types import DBHandler, DBHandlerResponse, DBHandlerStatus
label_desc: Use image node_id 7 for calling the SlackHandler obj's underlying member method code with example usage: obj.post_message(message) and returns: DBHandlerResponse, DBHandlerResponse