I want the Go client to support multi-key existence checks from an existing connected client with func…

I want the Go client to support multi-key existence checks from an existing connected client with func…: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). I want the Go client to support multi-key existence checks from an existing connected client with func (clnt Client)…