code: def forward_gpu(self, x):
      self.retain_inputs((0,))
      return (cuda.cupy.log(x[0]),)
  
imports: import math
  import numpy
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
  import chainerx
label_desc: Use image node_id 5 for calling the Log obj's underlying member method code with example usage: obj.forward_gpu(x) and returns: cuda