class_docstr: Exponential Linear Unit.
class_docstr_tok: ["Exponential","Linear","Unit","."]
code: def backward(self, indexes, grad_outputs):
      (y,) = self.get_retained_outputs()
      if self.alpha < 0:
          (cond,) = self.get_retained_inputs()
      else:
          cond = y
      (gy,) = grad_outputs
      return (ELUGrad(self.alpha, cond.array).apply((y,))[0] * gy,)
  
file_path: chainer/chainer/functions/activation/elu.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 5 for calling the ELU obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: unknown