public function addSelection()
    {
        $this->selection = $this->table->addColumn(null, 'CheckBox');

        // Move element to the beginning
        $k = array_search($this->selection, $this->table->columns);
        $this->table->columns = [$k => $this->table->columns[$k]] + $this->table->columns;

        return $this->selection;
    }