@Documented
 @Target(value=TYPE)
 @Retention(value=RUNTIME)
 @InterfaceAudience.Public
 @InterfaceStability.Evolving
public @interface Checkpointable
Contract representing to the framework that the task can be safely preempted
 and restarted between invocations of the user-defined function.
 This is often true when the result of a function does not rely on state
 derived from previous elements in the record stream, but the guarantee is
 left as an exercise to the implementor.