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 __init__(self, store_key):
      if not store_key:
          raise ValueError(
              "Invalid store_key. The store_key is a concatenation of "
              "'group_name' and the 'communicator_key'. See the "
              "docstring of `get_nccl_communicator` for details."
          )
      self._store_key = store_key
      self._store_name = None
      self._store = None
  
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 1 to create a new Rendezvous object  with example: obj = Rendezvous(store_key)