presto-ml/src/main/java/io/prestosql/plugin/ml/StringClassifierAdapter.java/StringClassifierAdapter/getSerializedData
class StringClassifierAdapter:    @Override
    public byte[] getSerializedData()
    {
        byte[] classifierBytes = serialize(classifier).getBytes();
        DynamicSliceOutput output = new DynamicSliceOutput(classifierBytes.length + 64 * labelEnumeration.size());
        output.appendInt(classifierBytes.length);
        output.appendBytes(classifierBytes);
        output.appendInt(labelEnumeration.size());
        // Write the enumeration keys
        for (Map.Entry<Integer, String> entry : labelEnumeration.entrySet()) {
            output.appendInt(entry.getKey());
            byte[] bytes = entry.getValue().getBytes(UTF_8);
            output.appendInt(bytes.length);
            output.appendBytes(bytes);
        }

        return output.slice().getBytes();
    }