// shape. The variant type should hold a TensorList.
    auto proto_attr = op.getValue().dyn_cast<TF::TensorProtoAttr>();
    if (!proto_attr) return failure();
    tensorflow::Tensor tensor;
    if (!tensorflow::ConvertToTensor(proto_attr, &tensor).ok())
      return failure();
    if (tensor.dtype() != tensorflow::DT_VARIANT) return failure();
    if (!tensorflow::TensorShapeUtils::IsScalar(tensor.shape()))
      return failure();