class_docstr: Strategy for training multiple TPU devices using the :func:`torch_xla.distributed.xla_multiprocessing.spawn`
  method.
code: def all_reduce(
      self,
      output: Union[Tensor, Any],
      group: Optional[Any] = None,
      reduce_op: Optional[Union[ReduceOp, str]] = None,
  ) -> Tensor:
      if not isinstance(output, Tensor):
          output = torch.tensor(output, device=self.root_device)
  
      invalid_reduce_op = (
          isinstance(reduce_op, ReduceOp) and reduce_op != ReduceOp.SUM
      )
      invalid_reduce_op_str = isinstance(
          reduce_op, str
      ) and reduce_op.lower() not in ("sum", "mean", "avg")
      if invalid_reduce_op or invalid_reduce_op_str:
          raise ValueError(
              "Currently, the XLAStrategy only supports `sum`, `mean`, `avg` for the reduce operation, got:"
              f" {reduce_op}"
          )
      import torch_xla.core.xla_model as xm
  
      output = xm.mesh_reduce("reduce", output, sum)
  
      if isinstance(reduce_op, str) and reduce_op.lower() in (
          "avg",
          "mean",
      ):
          output = output / self.world_size
  
      return output
  
imports: import io
  from typing import TYPE_CHECKING, Any, Callable, Dict, List, Optional, Union
  import torch
  from torch import Tensor
  from torch.nn import Module
  from torch.optim import Optimizer
  from torch.utils.data import DataLoader
  from typing_extensions import override
  from lightning.fabric.accelerators import Accelerator
  from lightning.fabric.accelerators.xla import _XLA_GREATER_EQUAL_2_1
  from lightning.fabric.plugins import XLAPrecision
  from lightning.fabric.plugins.environments import XLAEnvironment
  from lightning.fabric.plugins.io.xla import XLACheckpointIO
  from lightning.fabric.strategies import ParallelStrategy, _StrategyRegistry
  from lightning.fabric.strategies.launchers.xla import _XLALauncher
  from lightning.fabric.strategies.strategy import TBroadcast
  from lightning.fabric.utilities.rank_zero import rank_zero_only
  from lightning.fabric.utilities.types import _PATH, ReduceOp
label_desc: Use image node_id 18 for calling the XLAStrategy obj's underlying member method code with example usage: obj.all_reduce(output, group, reduce_op) and returns: output