code: def flatten(x):
      """Flatten a given array into one dimension.
  
      Args:
          x (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
  
      Returns:
          ~chainer.Variable: Output variable flatten to one dimension.
  
      .. note::
  
          When you input a scalar array (i.e. the shape is ``()``),
          you can also get the one dimension array whose shape is ``(1,)``.
  
      .. admonition:: Example
  
          >>> x = np.array([[1, 2], [3, 4]])
          >>> x.shape
          (2, 2)
          >>> y = F.flatten(x)
          >>> y.shape
          (4,)
          >>> y.array
          array([1, 2, 3, 4])
  
          >>> x = np.arange(8).reshape(2, 2, 2)
          >>> x.shape
          (2, 2, 2)
          >>> y = F.flatten(x)
          >>> y.shape
          (8,)
          >>> y.array
          array([0, 1, 2, 3, 4, 5, 6, 7])
  
      """
      return chainer.functions.reshape(x, (x.size,))
  
label_desc: Use image node_id 1 for calling a global function with example usage: flatten(x) and returns: chainer