Ways of extending VL with custom transformations.
These are hooks for additional transforms that we use at Centaur, but which have not yet been released for whatever reason. When it comes time for us to run our transforms, we just defattach our implementations to these hooks. For non-Centaur users, these steps are just no-ops.
Some of these transforms will never be released because they're gross hacks that are intended to address Centaur-specific things, and they wouldn't be of any interest outside of Centaur. We may release the others eventually, but they may be in beta or tied into other libraries in a deep way that makes it hard to make them available at this time.