code: def forward(ctx, x):
      ctx.save_for_backward(x)
      return torch.exp(x)
  
imports: import torch
  from torch.autograd import Function
  from torch.cuda.amp import custom_bwd, custom_fwd
label_desc: Use image node_id 1 for calling the _trunc_exp obj's underlying member method code with example usage: obj.forward(ctx, x) and returns: torch