Platform 7 upgrade in progress: Learn about the first highlights and changes

Hi,

Anyone knows how to implement Attachment Text Extractor in Platform 7/Confluence 9

The steps in this tutorial
https://developer.atlassian.com/server/confluence/attachment-text-extractor-module-tutorial/
uses InputStreamSource from package com.atlassian.confluence.util.io

This package is showing a warning that package com.atlassian.confluence.util.io is not available.

WARN [main] [hook.dmz.DmzResolverHook] filterMatches Package com.atlassian.confluence.util.io is internal and is not available for export to plugin 

Thanks