class_docstr: A customized communication operation which forward is all_reduce operation,
  backward is an identity operation.
  
  Args:
      input_: input matrix.
      comm_spec: comm_spec will give information like process group, rank list, etc.
class_docstr_tok: ["A","customized","communication","operation","which","forward","is","all_reduce","operation",",","backward","is","an","identity","operation",".","Args",":","input_",":","input","matrix",".","comm_spec",":","comm_spec","will","give","information","like","process","group",",","rank","list",",","etc","."]
code: def forward(ctx, input_, comm_spec):
      return _all_reduce(input_, comm_spec)
  
imports: import operator
  from enum import Enum
  from functools import reduce
  import torch
  import torch.distributed
  from torch.distributed import ReduceOp
label_desc: Use image node_id 2 for calling the _ReduceInput obj's underlying member method code with example usage: obj.forward(ctx, input_, comm_spec) and returns: _all_reduce