class_docstr: Softplus function.
class_docstr_tok: ["Softplus","function","."]
code: def forward_gpu(self, inputs):
      self.retain_inputs((0,))
      x = inputs[0]
      y = cuda.elementwise(
          "T x, T beta, T beta_inv",
          "T y",
          """
                T bx = beta * x;
                y = (max(bx, (T)0) + log1p(exp(-fabs(bx)))) * beta_inv;
              """,
          "softplus_fwd",
      )(x, self.beta, self.beta_inv)
      return (y,)
  
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 4 for calling the Softplus obj's underlying member method code with example usage: obj.forward_gpu(inputs) and returns: y