public function columns($columns = [])
    {
        if (func_num_args() == 0) {
            return $this->columns;
        }

        if (func_num_args() == 1 && is_array($columns)) {
            foreach ($columns as $column => $label) {
                $this->column($column, $label);
            }

            return;
        }

        foreach (func_get_args() as $column) {
            $this->column($column);
        }
    }