code: def backward(ctx, grad_o):
      grads = mlp_cuda.backward(
          ctx.bias,
          ctx.activation,
          grad_o,
          ctx.outputs,
          ctx.saved_tensors,
      )
      del ctx.outputs
      return (None, None, *grads)
  
file_path: apex/apex/mlp/mlp.py
imports: from copy import copy
  import math
  import torch
  from torch import nn
  from apex._autocast_utils import _cast_if_autocast_enabled
  import mlp_cuda
label_desc: Use image node_id 2 for calling the MlpFunction obj's underlying member method code with example usage: obj.backward(ctx, grad_o) and returns: None,  None,  unknown