code: def _sigmoid_grad(x, y, gy):
      return chainer.functions.activation.sigmoid.SigmoidGrad(
          (x,)
      ).apply((y, gy))[0]
  
imports: import numpy
  import six
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function_node
  from chainer import utils
  from chainer.utils import argument
  from chainer.utils import precision
  from chainer.utils import type_check
label_desc: Use image node_id 1 for calling a global function with example usage: _sigmoid_grad(x, y, gy) and returns: chainer