If there is likely to be code that gets broken by this, we could keep supporting the old attachementsIds, while still switching the docs and preferred usage to either "fileHandles" or "attachmentFileHandleIds" whichever you guys like better. It looks like the Python client is a bit divergent from the R client here already, according the to [C4 document](https://sagebionetworks.jira.com/wiki/pages/viewpage.action?pageId=34373660), but in a good way -- extra functionality.