code: def hstack(xs):
      """Concatenate variables horizontally (column wise).
  
      Args:
          xs (list of :class:`~chainer.Variable` or :ref:`ndarray`):
              Input variables to be concatenated. The variables must have the
              same ``ndim``. When the variables have the second axis (i.e.
              :math:`ndim \\geq 2`), the variables must have the same shape
              along all but the second axis. When the variables do not have the
              second axis(i.e. :math:`ndim < 2`), the variables need not to have
              the same shape.
  
      Returns:
          ~chainer.Variable:
              Output variable. When the input variables have the second axis
              (i.e. :math:`ndim \\geq 2`), the shapes of inputs and output are
              the same along all but the second axis. The length of second axis
              is the sum of the lengths of inputs' second axis.
              When the variables do not have the second axis (i.e.
              :math:`ndim < 2`), the shape of output is ``(N, )`` (``N`` is the
              sum of the input variables' size).
  
      .. admonition:: Example
  
          >>> x1 = np.array((1, 2, 3))
          >>> x1.shape
          (3,)
          >>> x2 = np.array((2, 3, 4))
          >>> x2.shape
          (3,)
          >>> y = F.hstack((x1, x2))
          >>> y.shape
          (6,)
          >>> y.array
          array([1, 2, 3, 2, 3, 4])
          >>> x1 = np.arange(0, 12).reshape(3, 4)
          >>> x1.shape
          (3, 4)
          >>> x1
          array([[ 0,  1,  2,  3],
                 [ 4,  5,  6,  7],
                 [ 8,  9, 10, 11]])
          >>> x2 = np.arange(12, 18).reshape(3, 2)
          >>> x2.shape
          (3, 2)
          >>> x2
          array([[12, 13],
                 [14, 15],
                 [16, 17]])
          >>> y = F.hstack([x1, x2])
          >>> y.shape
          (3, 6)
          >>> y.array
          array([[ 0,  1,  2,  3, 12, 13],
                 [ 4,  5,  6,  7, 14, 15],
                 [ 8,  9, 10, 11, 16, 17]])
  
      """
  
      (y,) = Hstack().apply(xs)
      return y
  
file_path: chainer/chainer/functions/array/hstack.py
imports: import numpy
  import six
  import chainer
  from chainer import backend
  from chainer import function_node
  from chainer.utils import type_check
label_desc: Use image node_id 1 for calling a global function with example usage: hstack(xs) and returns: y