code: def backward(ctx, grad_output):
      i = ctx.saved_tensors[0]
      sigmoid_i = torch.sigmoid(i)
      return grad_output * (sigmoid_i * (1 + i * (1 - sigmoid_i)))
  
imports: import re
  import math
  import collections
  from functools import partial
  import torch
  from torch import nn
  from torch.nn import functional
  from torch.utils import model_zoo
label_desc: Use image node_id 2 for calling the SwishImplementation obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: unknown