private Tensor evaluate(String expr, Tensor x, Tensor y) throws ParseException {
        return evaluate(expr, x, y, null);
    }
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