class_docstr: Zoneout regularization.
class_docstr_tok: ["Zoneout","regularization","."]
code: def backward(self, indexes, grad_outputs):
      (gy,) = grad_outputs
      ret = []
      if 0 in indexes:
          ret.append(gy * self.flag_h)
      if 1 in indexes:
          ret.append(gy * self.flag_x)
      return ret
  
file_path: chainer/chainer/functions/noise/zoneout.py
imports: import numpy
  from chainer import backend
  from chainer import configuration
  from chainer import function_node
  from chainer.utils import argument
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the Zoneout obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: ret