The completer Completion API has seen an overhaul. The old Completer.complete() API is waiting deprecation and will soon be replaced by the Completer.completions() one. While the Completer.complete() API was assuming completions would all replace the same range of text in the completed buffer, Completer.completions() does not. To smooth the transition we provide two utility methods regulrize... and stufff which can partially adapt between the old and new API. The new API is marked as "unstable" and can only be use explicitly when called from within a decorator we provide.