code: def num_alive_nodes():
      n = 0
      for node in ray.nodes():
          if node["Alive"]:
              n += 1
      return n
  
file_path: ray/release/benchmarks/object_store/test_object_store.py
imports: import numpy
  import ray
  import ray.autoscaler.sdk
  import json
  import os
  from time import perf_counter
  from tqdm import tqdm
label_desc: Use image node_id 1 for calling a global function with example usage: num_alive_nodes() and returns: n