public Set<String> getOutputs() {
        return outputs.keySet();
    }
Model information (input and output types) for an ONNX model.
This encapsulates the difference between reading ONNX model information
- from a file application package, where we can read the ONNX model directly
- from a ZK application package, where the file is unavailable and models are read from
  generated files stored in file distribution or ZooKeeper.

@author lesters
config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelInfo.java