code: def test_allmask_backward(self):
      self.test_backward(True)
  
imports: import itertools
  import torch
  from torch.testing._internal import common_utils
  from apex.transformer import AttnMaskType
  from apex.transformer.functional import FusedScaleMaskSoftmax
label_desc: Use image node_id 6 for calling the TestGenericFusedSoftmaxKernel obj's underlying member method code with example usage: obj.test_allmask_backward() without return types