func KeyExists(key string) clientv3.Cmp {
	return clientv3.Compare(clientv3.Version(key), ">", 0)
}
func KeyExists(key string) clientv3.Cmp {
	return clientv3.Compare(clientv3.Version(key), ">", 0)
}
// KeyExists returns a comparison operation that evaluates to true iff the given
// key exists. It does this by checking if the key `Version` is greater than 0.
// It is a useful guard in transaction delete operations.