private static Optional<Onnx.NodeProto> getNodeFromGraphOutputs(String nodeName, Onnx.GraphProto graph) {
        return graph.getNodeList().stream().filter(node ->
                node.getOutputList().stream().anyMatch(name -> name.equals(nodeName))).findFirst();
    }
Converts an ONNX graph to a Vespa IntermediateGraph which is the basis
for generating Vespa ranking expressions.

@author lesters
model-integration/src/main/java/ai/vespa/rankingexpression/importer/onnx/GraphImporter.java