code: def backward(ctx, grad_output):
      x = ctx.saved_tensors[0]
      sx = torch.sigmoid(x)  # sigmoid(ctx)
      return grad_output * (sx * (1 + x * (1 - sx)))
  
imports: import torch.nn.functional
  from .utils import *
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