code: def forward(ctx, input_, comm_spec):
      ctx.comm_spec = comm_spec
      return _mix_gather(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 _MixGatherForwardMixSplitBackward obj's underlying member method code with example usage: obj.forward(ctx, input_, comm_spec) and returns: _mix_gather