UpdateStrategy rest.RESTUpdateStrategy
	// BeginUpdate is an optional hook that returns a "transaction-like"
	// commit/revert function which will be called at the end of the operation,
	// but before AfterUpdate and Decorator, indicating via the argument
	// whether the operation succeeded.  If this returns an error, the function
	// is not called.  Almost nobody should use this hook.
	BeginUpdate BeginUpdateFunc