code: def report_world_size(self, group_name="default"):
      ws = col.get_collective_group_size(group_name)
      return ws
  
imports: import cupy
  import logging
  import ray
  import ray.util.collective
  from ray.util.collective.types import Backend, ReduceOp
  from ray.util.collective.collective_group.nccl_util import get_num_gpus
  import torch
label_desc: Use image node_id 17 for calling the MultiGPUWorker obj's underlying member method code with example usage: obj.report_world_size(group_name) and returns: ws