Attributes attr(String name, int [] vals) {
            Onnx.AttributeProto.Builder builder = Onnx.AttributeProto.newBuilder();
            for (int val : vals) {
                builder.addInts(val);
            }
            nodeBuilder.addAttribute(builder.setName(name).setType(INTS).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