public function deleteBatch(array $keys, array $options = [])
    {
        $options += [
            'baseVersion' => null
        ];

        $mutations = [];
        foreach ($keys as $key) {
            $mutations[] = $this->operation->mutation('delete', $key, Key::class, $options['baseVersion']);
        }

        return $this->operation->commit($mutations, $options);
    }