presto-rcfile/src/main/java/io/prestosql/rcfile/text/MapEncoding.java/MapEncoding/MapEncoding
class MapEncoding:    public MapEncoding(Type type, Slice nullSequence,
            byte[] separators,
            Byte escapeByte,
            TextColumnEncoding keyEncoding,
            TextColumnEncoding valueEncoding)
    {
        super(type, nullSequence, separators, escapeByte);
        this.keyEncoding = keyEncoding;
        this.valueEncoding = valueEncoding;
    }