In 0.5.0 or earlier releases, PipelineRunner provides an apply(PTransform<InputT, OutputT>, InputT) method which allows runner implementation to perform actions when the PTransform is added to the pipeline. In later releases, that apply(...) method has been replaced by a Pipeline#replaceAll() method, where the runner can only get involved after the pipeline has been fully constructed. In terms of override PTransforms, these two APIs are identical. But, the early API could still be helpful. For example, the runner could remember the line at which the PTransform was added, and provide that info to users to assist debugging. Is it possible to add that API back? Or is there any other way to involve the runner when a PTransform is added?
Thanks, Shen
