pinned property
Whether this revision is pinned to prevent automatic purging.
If not set, the revision is automatically purged 30 days after newer content is uploaded. This field can only be modified on files with content stored in Drive, excluding Docs Editors files. Revisions can also be pinned when they are created through the drive.files.insert/update/copy by using the pinned query parameter. Pinned revisions are stored indefinitely using additional storage quota, up to a maximum of 200 revisions.
Implementation
core.bool? pinned;