code: def forward(ctx, input_, reduce_mean: bool = False):
      output = all_reduce(input_, ParallelMode.PARALLEL_2P5D_COL)
      ctx.reduce_mean = reduce_mean
      if reduce_mean:
          reduce_size = gpc.get_world_size(
              ParallelMode.PARALLEL_2P5D_COL
          )
          ctx.reduce_size = reduce_size
          return output.clone() / reduce_size
      return output.clone()
  
imports: from typing import Any, Tuple
  import torch
  import torch.distributed
  from torch import Tensor
  from torch.cuda.amp import custom_bwd, custom_fwd
  from colossalai.legacy.communication.collective import all_gather, all_reduce, reduce_scatter
  from colossalai.legacy.context.parallel_mode import ParallelMode
  from colossalai.legacy.core import global_context
  from colossalai.utils import get_current_device
label_desc: Use image node_id 2 for calling the _RreduceByBatch2p5D obj's underlying member method code with example usage: obj.forward(ctx, input_, reduce_mean) and returns: output, unknown