code: def forward_gpu(self, x):
      self.retain_outputs((0,))
      return (cuda.cupy.expm1(x[0]),)
  
file_path: chainer/chainer/functions/math/exponential_m1.py
imports: import numpy
  from chainer.backends import cuda
  from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the Expm1 obj's underlying member method code with example usage: obj.forward_gpu(x) and returns: cuda