if (localForeignFields) {
        std::tie(_localField, _foreignField) = *localForeignFields;
 }

 // Handle subpipeline's first stage self-applies the view def.
 if (shouldDiscardViewPrefix(_fromNsIsAView, pipeline, subpipelineViewPolicy, expCtx.get())) {
        handleSelfApplyingViewStage(fromNs, pipeline, expCtx.get());
        return;
 }

 // Prepend view def and build pipeline.
 handleStandardViewResolution(pipeline, localForeignFields.has_value());