presto-rcfile/src/main/java/io/prestosql/rcfile/binary/BinaryRcFileEncoding.java/BinaryRcFileEncoding/mapEncoding
class BinaryRcFileEncoding:    @Override
    public ColumnEncoding mapEncoding(Type type, ColumnEncoding keyEncoding, ColumnEncoding valueEncoding)
    {
        return new MapEncoding(
                type,
                (BinaryColumnEncoding) keyEncoding,
                (BinaryColumnEncoding) valueEncoding);
    }