@Documented
 @Retention(value=RUNTIME)
 @Target(value=PARAMETER)
public static @interface DoFn.Restriction
DoFn.GetSize, DoFn.SplitRestriction, DoFn.GetInitialWatermarkEstimatorState, DoFn.NewWatermarkEstimator, and DoFn.NewTracker
 methods. Must match the return type used on the method annotated with DoFn.GetInitialRestriction.