@Documented
 @Retention(value=RUNTIME)
 @Target(value=METHOD)
public static @interface DoFn.GetWatermarkEstimatorStateCoder
DoFn.
 If not defined, a coder will be inferred using standard coder inference rules and the
 pipeline's coder registry.
 
This method will be called only at pipeline construction time.
Signature: Coder<WatermarkEstimatorStateT> getWatermarkEstimatorStateCoder();