private TensorFunction<Reference> optimizeAndRename(String opName, IntermediateOperation op) {
        IntermediateGraph graph = new IntermediateGraph(modelName);
        graph.put(opName, op);
        graph.outputs(graph.defaultSignature()).put(opName, opName);
        graph.optimize();
        return op.function().get();
    }
Unit tests for ONNX operators. The number on the test reflects the minimum
opset number for the operations tested.

@author lesters
model-integration/src/test/java/ai/vespa/rankingexpression/importer/onnx/OnnxOperationsTestCase.java