code: def backward_preprocess(self, function, in_data, out_grad):
      cuda.cupy.cuda.nvtx.RangePush(function.label + ".backward")
  
file_path: chainer/chainer/function_hooks/cuda_profile.py
imports: from chainer.backends import cuda
  from chainer import function_hook
label_desc: Use image node_id 4 for calling the CUDAProfileHook obj's underlying member method code with example usage: obj.backward_preprocess(function, in_data, out_grad) without return types