if (req.IsValid()) return values(req);

  return nullptr;
}

// Context used during ShapeInference. This class contains common information
// that is required by the individual shape inference helper functions (e.g.,
// TF Graph version, constant values computed, etc.)
class ShapeInference {
 public:
  ShapeInference(int64_t graph_version, ModuleOp module,
                 bool propagate_caller_callee_constants,