public PipelineStepRequest build() {
            return new PipelineStepRequest(
                    sessionUuid,
                    criteria,
                    childStreamType,
                    stepLocation,
                    stepType,
                    stepFilterMap,
                    pipeline,
                    code,
                    stepSize,
                    timeout);
        }
This is what chooses the input to the translation.
stroom-core-shared/src/main/java/stroom/pipeline/shared/stepping/PipelineStepRequest.java