how to insert column with calculated

<?php
//Step 1: Load KoolReport
require_once "../../../load.koolreport.php";
use \koolreport\pivot\processes\Pivot;
use \koolreport\pivot\processes\PivotExtract;
use \koolreport\processes\ColumnMeta;
use \koolreport\processes\Filter;
use \koolreport\processes\calculatedcolumn;

//Step 2: Creating Report class
class MyReport extends \koolreport\KoolReport
{
    function settings()
    {
        $config = include "../../../config.php";
        return array(
            "dataSources" => array(
                "laporan"=>$config["laporan"]
                 )         
       );
    }

    public function setup()
    {
        $this->src('laporan')
        ->query("select * from kegiatan")
        ->pipe(new pivot(array(
            "dimensions" => array(
                "column" => "kdbeban", 
                "row" => "kdgiat, kdoutput, kdkmpnen, kdskmpnen, kdakun",
            ),
            "aggregates" => array(
                "sum" => "pagu, realisasi", 
        ),
        )))->saveto($source);

        $source->pipe($this->datastore('lapkeg'));
 
    }
}