static Optional<Reference> parseOnnxInput(String input) {
        var optRef = Reference.simple(input);
        if (optRef.isPresent()) {
            return optRef;
        }
        try {
            var ref = Reference.fromIdentifier(input);
            return Optional.of(ref);
        } catch (Exception e) {
            // fallthrough
        }
        return Optional.empty();
    }
make it possible to evaluate an ONNX model anywhere in the ranking expression tree
model-evaluation/src/main/java/ai/vespa/models/evaluation/OnnxExpressionNode.java