public function addFlag(string $name): void
    {
        if (!$this->hasFlag($name)) {
            $flagEntry = $this->entry[PoTokens::FLAG];
            if ($flagEntry === null) {
                $this->set(PoTokens::FLAG, $name);
            } elseif (is_array($flagEntry)) {
                $flagEntry[] = $name;
                $this->set(PoTokens::FLAG, implode(',', $flagEntry));
            } else {
                $this->set(PoTokens::FLAG, $flagEntry . ',' . $name);
            }
        }
    }