code: def sigmoid(x):
      """Element-wise sigmoid logistic function.
  
       .. math:: f(x)=(1 + \\exp(-x))^{-1}.
  
      Args:
          x (:class:`~chainer.Variable` or :ref:`ndarray`):
              Input variable. A :math:`(s_1, s_2, ..., s_N)`-shaped float array.
  
      Returns:
          ~chainer.Variable: Output variable. A
          :math:`(s_1, s_2, ..., s_N)`-shaped float array.
  
      .. admonition:: Example
  
          It maps the input values into the range of :math:`[0, 1]`.
  
          >>> x = np.arange(-2, 3, 2).astype(np.float32)
          >>> x
          array([-2.,  0.,  2.], dtype=float32)
          >>> F.sigmoid(x).array
          array([0.11920291, 0.5       , 0.8807971 ], dtype=float32)
  
      """
      (y,) = Sigmoid().apply((x,))
      return y
  
imports: import numpy
  import chainer
  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 1 for calling a global function with example usage: sigmoid(x) and returns: y