code: def test_allreduce_once(n_clients, n_aux):
      _test_allreduce_once(n_clients, n_aux)
  
imports: import random
  import time
  import numpy
  import pytest
  import torch
  import hivemind
  from hivemind.averaging import DecentralizedAverager
  from hivemind.averaging.allreduce import AveragingMode
  from hivemind.averaging.control import AveragingStage
  from hivemind.averaging.key_manager import GroupKeyManager
  from hivemind.averaging.load_balancing import load_balance_peers
  from hivemind.averaging.partition import AllreduceException
  from hivemind.p2p import PeerID
  from test_utils.dht_swarms import launch_dht_instances
label_desc: Use image node_id 2 for calling a global function with example usage: test_allreduce_once(n_clients, n_aux) without return types