code: def test_ckpt_arg_none(self, mask):
      module = DropMaskLinear(HIDDEN_DIM, HIDDEN_DIM)
      inputs = (torch.rand(HIDDEN_DIM), None)
      inputs[0].requires_grad = True
      _test_activation_checkpoint(module, *inputs)
  
imports: import pytest
  import torch
  import deepspeed
  from deepspeed.accelerator import get_accelerator
  from copy import deepcopy
  from unit.common import DistributedTest
label_desc: Use image node_id 5 for calling the TestActivationCheckpoint obj's underlying member method code with example usage: obj.test_ckpt_arg_none(mask) without return types