@SuppressWarnings("unchecked") public GrAggBuilder(StageWithKeyAndWindow<?, K> stage) { ComputeStageImplBase computeStage = ((StageWithGroupingBase) stage).computeStage; ensureJetEvents(computeStage, "This pipeline stage"); pipelineImpl = (PipelineImpl) computeStage.getPipeline(); wDef = stage.windowDefinition(); upstreamStages.add(computeStage); keyFns.add(stage.keyFn()); }