I want to know how file_annotation parameter works with chat_postMessage method. I already search it on issue and the document of the chat_postMessage method, but there was no appropriate information about it.

    def chat_postMessage(
        self,
        *,
        channel: str,
        text: Optional[str] = None,
        ...
        file_annotation: Optional[str] = None, # > How can I use this? 
        ...
        **kwargs,
    ) -> SlackResponse:

In my case, I use bolt SDK to handle the message events on socket mode, and want to send message to another channels if the message was sent by a user. However, if the file is attached to the origin message, there was no ways to send the same file to the bot message, which was sent by bot with bolt SDK.

I assume to use the file_annotation parameter in the chat_postMessage method, but there was no information to teach how it works. Isn't is supported yet?