public function addList($name, array $values, array $columns = null, $showHeaders = null)
    {
        $this->fields[] = '--add-list=' . $name;

        $this->fields[] = '--list-values=' . implode('|', $values);

        // columns given => show headers if it's not explicitly disabled
        if ($columns !== null && $showHeaders === null) {
            $showHeaders = true;
        }

        if ($showHeaders) {
            $this->fields[] = '--show-header';
        }

        if ($columns !== null) {
            $this->fields[] = '--column-values=' . implode('|', $columns);
        }

        return $this;
    }