code: def _sigmoid(x):
      xp = backend.get_array_module(x)
      half = x.dtype.type(0.5)
      return xp.tanh(x * half) * half + half
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 1 for calling a global function with example usage: _sigmoid(x) and returns: unknown