code: def forward(self, x):
      if self.training and using_ckpt:
          return checkpoint(self.forward_impl, x)
      else:
          return self.forward_impl(x)
  
imports: import torch
  from torch import nn
  from torch.utils.checkpoint import checkpoint
label_desc: Use image node_id 3 for calling the IBasicBlock obj's underlying member method code with example usage: obj.forward(x) and returns: checkpoint, self