docstr: This communication hook is for illustration and testing purposes only.
  This communication hook is used during FSDP ``FULL_SHARD`` or ``SHARD_GRAD_OP`` training.
  It adds some noise to the provided ``grad`` parameter, uses
  ``reduce_scatter`` for gradient communication and stores a sharded gradient in ``output``.
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code: def dummy_hook_for_sharded_fsdp(
      self, state: DummyState, grad: torch.Tensor, output: torch.Tensor
  ):
      """
      This communication hook is for illustration and testing purposes only.
      This communication hook is used during FSDP ``FULL_SHARD`` or ``SHARD_GRAD_OP`` training.
      It adds some noise to the provided ``grad`` parameter, uses
      ``reduce_scatter`` for gradient communication and stores a sharded gradient in ``output``.
      """
      grad.add_(state.noise)
      self.custom_reduce_scatter(
          output, grad, group=state.process_group
      )
  
imports: import sys
  from typing import Optional
  import torch
  import torch.nn
  import torch.nn.functional
  from torch import distributed
  from torch.distributed.algorithms._comm_hooks import default_hooks
  from torch.distributed.distributed_c10d import _get_default_group
  from torch.distributed.fsdp import FullyShardedDataParallel, MixedPrecision
  from torch.distributed.fsdp.fully_sharded_data_parallel import ShardingStrategy
  from torch.distributed.fsdp.wrap import ModuleWrapPolicy
  from torch.testing._internal.common_distributed import requires_nccl, requires_nccl_version, skip_but_pass_in_sandcastle_if, skip_if_lt_x_gpu
  from torch.testing._internal.common_fsdp import FSDPTest
  from torch.testing._internal.common_utils import instantiate_parametrized_tests, parametrize, run_tests
label_desc: Use image node_id 3 for calling the DummyHook obj's underlying member method code with example usage: obj.dummy_hook_for_sharded_fsdp(state, grad, output) without return types