code: def forward(self, x):
      x = checkpoint(self.mlp_1, x)
      x = checkpoint(self.mlp_2, x)
      x = self.output(x)
      return x
  
file_path: ColossalAI/tests/test_fx/test_tracer/test_activation_checkpoint_annotation.py
imports: import torch
  from torch.fx import GraphModule
  from torch.utils.checkpoint import checkpoint
  from colossalai.fx import ColoTracer
  from colossalai.testing import clear_cache_before_run
label_desc: Use image node_id 2 for calling the MyModule obj's underlying member method code with example usage: obj.forward(x) and returns: x