class_docstr: A backward trigger function.
class_docstr_tok: ["A","backward","trigger","function","."]
docstr: We return zero grad for the trigger only.
docstr_tok: ["We","return","zero","grad","for","the","trigger","only","."]
code: def backward(ctx: Any, *args: Any) -> Any:
      """We return zero grad for the trigger only."""
      if DEBUG and dist.is_initialized() and dist.get_rank() == 0:
          print("DEBUG trigger bwd")
      assert len(args) == 1
      w, trigger = ctx.saved_tensors
      assert w.requires_grad
      assert trigger.requires_grad
      return None, torch.zeros_like(trigger)
  
imports: from typing import Any, Optional, Tuple
  import torch
  from torch import nn
  import torch.distributed
  import torch.nn.functional
label_desc: Use image node_id 2 for calling the BackwardTriggerFn obj's underlying member method code with example usage: obj.backward(ctx) and returns: None,  torch