presto-ml/src/main/java/io/prestosql/plugin/ml/StringClassifierAdapter.java/StringClassifierAdapter/classify
class StringClassifierAdapter:    @Override
    public String classify(FeatureVector features)
    {
        int prediction = classifier.classify(features);
        checkState(labelEnumeration.containsKey(prediction), "classifier predicted an unknown class %s", prediction);
        return labelEnumeration.get(prediction);
    }