presto-main/src/main/java/io/prestosql/type/setdigest/SetDigestType.java/SetDigestType/getObjectValue
class SetDigestType:    @Override
    public Object getObjectValue(ConnectorSession session, Block block, int position)
    {
        if (block.isNull(position)) {
            return null;
        }

        return new SqlVarbinary(block.getSlice(position, 0, block.getSliceLength(position)).getBytes());
    }