private static void verifyNoWarnings(IntermediateGraph intermediateGraph) {
        for (java.util.Map.Entry<String, String> output : intermediateGraph.outputs(intermediateGraph.defaultSignature()).entrySet()) {
            IntermediateOperation operation = intermediateGraph.get(output.getValue());
            Set<String> warnings = getWarnings(operation);
            if (warnings.size() > 0) {
                throw new IllegalArgumentException("Could not import " + intermediateGraph.name() + ": " + String.join("\n", warnings));
            }
        }
    }
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