code: def do_allreduce(self, group_name="default", op=ReduceOp.SUM):
      col.allreduce(self.buffer, group_name, op)
      return self.buffer
  
imports: import numpy
  import logging
  import ray
  import ray.util.collective
  from ray.util.collective.types import Backend, ReduceOp
  import torch
label_desc: Use image node_id 7 for calling the Worker obj's underlying member method code with example usage: obj.do_allreduce(group_name, op) and returns: self