class_docstr: Softplus function.
class_docstr_tok: ["Softplus","function","."]
code: def backward(self, indexes, grad_outputs):
      x = self.get_retained_inputs()[0]
      (gy,) = grad_outputs
      return SoftplusGrad((self.beta,)).apply((x, gy))
  
imports: import numpy
  from chainer.backends import cuda
  from chainer import function_node
  import chainer.functions
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 5 for calling the Softplus obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: SoftplusGrad