class_docstr: A rendezvous class for different actor/task processes to meet.
  
  To initialize an NCCL collective communication group, different
  actors/tasks spawned in Ray in a collective group needs to meet
  each other to synchronize the NCCLUniqueID. This class guarantees
  they meet via the NCCLUniqueIDStore, initialized on the rank=0
  process.
  
  Args:
      store_key: the unique store key, usually as a concatanation
          of group_name and communicator key. See `get_nccl_communicator`
          for more details.
code: def store(self):
      return self._store
  
imports: import logging
  import datetime
  import time
  import ray
  import cupy
  from ray.util.collective.const import ENV
  from ray.util.collective.collective_group import nccl_util
  from ray.util.collective.collective_group.base_collective_group import BaseGroup
  from ray.util.collective.const import get_store_name
  from ray.util.collective.types import AllReduceOptions, BarrierOptions, Backend, ReduceOptions, BroadcastOptions, AllGatherOptions, ReduceScatterOptions, SendOptions, RecvOptions
  from ray.util.collective.collective_group.cuda_stream import get_stream_pool
label_desc: Use image node_id 3 for calling the Rendezvous obj's underlying member method code with example usage: obj.store() and returns: self