code: def _forward(self, *args, **kwargs):
      raise NotImplementedError(
          "CheckpointModule should implement _forward method instead of origin forward"
      )
  
file_path: ColossalAI/tests/kit/model_zoo/custom/base.py
imports: import torch.nn
  from torch.utils.checkpoint import checkpoint
label_desc: Use image node_id 2 for calling the CheckpointModule obj's underlying member method code with example usage: obj._forward() without return types