docstr: Blocks until all processes reach this barrier.
  
  Args:
      barrier_options: barrier options.
  
  Returns:
      None
docstr_tok: ["Blocks","until","all","processes","reach","this","barrier",".","Args",":","barrier_options",":","barrier","options",".","Returns",":","None"]
code: def barrier(self, barrier_options=BarrierOptions()):
      """Blocks until all processes reach this barrier.
  
      Args:
          barrier_options: barrier options.
  
      Returns:
          None
      """
      # Get the device list.
      if self._used_gpu_indices:
          devices = list(self._used_gpu_indices)
      else:
          devices = list(range(nccl_util.get_num_gpus()))
      barrier_tensors = [None] * len(devices)
      for i, d in enumerate(devices):
          with nccl_util.Device(d):
              barrier_tensors[i] = cupy.array([1])
      self.allreduce(barrier_tensors)
  
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 5 for calling the NCCLGroup obj's underlying member method code with example usage: obj.barrier(barrier_options) without return types