presto-ml/src/main/java/io/prestosql/plugin/ml/AbstractSvmModel.java/AbstractSvmModel/toSvmNodes
class AbstractSvmModel:    protected static svm_node[] toSvmNodes(FeatureVector features)
    {
        svm_node[] nodes = new svm_node[features.size()];
        int i = 0;
        // Features map is sorted, so we can just flatten it to a list for libsvm
        for (SortedMap.Entry<Integer, Double> feature : features.getFeatures().entrySet()) {
            nodes[i] = new svm_node();
            nodes[i].index = feature.getKey();
            nodes[i].value = feature.getValue();
            i++;
        }

        return nodes;
    }