Attributes attr(String name, int val) {
            nodeBuilder.addAttribute(Onnx.AttributeProto.newBuilder().setName(name).setType(INT).setI(val).build());
            return this;
        }
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