ExperimentalProtoLayoutExtensionApi
@RequiresOptIn(level = Level.ERROR)
@Retention(value = RetentionPolicy.CLASS)
@Target(value = [ElementType.METHOD, ElementType.TYPE, ElementType.FIELD])
annotation ExperimentalProtoLayoutExtensionApi
Denotes that this API surface is not usable by default and requires existence of an extension provider (on the rendering side).