code: def after(self, xs):
      return "gx = val;"
  
imports: import six
  from chainer.functions.pooling import pooling_nd_kernel
  from chainer.utils import conv_nd_kernel
label_desc: Use image node_id 5 for calling the MaxPoolingNDKernelBackward obj's underlying member method code with example usage: obj.after(xs) and returns: str