presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/serializers/MapLexicoder.java/MapLexicoder/encode
class MapLexicoder:    @Override
    public byte[] encode(Map<K, V> v)
    {
        byte[][] elements = new byte[v.size() * 2][];
        int index = 0;
        for (Entry<K, V> entry : v.entrySet()) {
            elements[index++] = escape(keyLexicoder.encode(entry.getKey()));
            elements[index++] = escape(valueLexicoder.encode(entry.getValue()));
        }

        return concat(elements);
    }