presto-ml/src/main/java/io/prestosql/plugin/ml/FeatureUnitNormalizer.java/FeatureUnitNormalizer/getSerializedData
class FeatureUnitNormalizer:    @Override
    public byte[] getSerializedData()
    {
        // Serialization format is (<key:int><min:double><max:double>)*
        SliceOutput output = Slices.allocate((SizeOf.SIZE_OF_INT + 2 * SizeOf.SIZE_OF_DOUBLE) * mins.size()).getOutput();
        for (int key : mins.keySet()) {
            output.appendInt(key);
            output.appendDouble(mins.get(key));
            output.appendDouble(maxs.get(key));
        }
        return output.slice().getBytes();
    }