class_docstr: Implementation of the Swish activation function: x * sigmoid(x).
  
  Searching for activation functions. Ramachandran, Prajit and Zoph, Barret
  and Le, Quoc V. 2017
code: def backward(ctx, grad_output):
      (x,) = ctx.saved_tensors
      sigmoid_x = torch.sigmoid(x)
      return grad_output * (sigmoid_x * (1 + x * (1 - sigmoid_x)))
  
file_path: pytorchvideo/pytorchvideo/layers/swish.py
imports: import torch
  import torch.nn
label_desc: Use image node_id 2 for calling the SwishFunction obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: unknown