private function formatPrecondition(array $options, $mustExist = false)
    {
        if (!isset($options['precondition']) && !$mustExist) {
            return $options;
        }

        $precondition = isset($options['precondition'])
            ? $options['precondition']
            : [];

        if (isset($precondition['updateTime'])) {
            return $options;
        }

        if ($mustExist) {
            $precondition['exists'] = true;
        }

        $options['precondition'] = $precondition;

        return $options;
    }