code: def polygamma(n, x):
      """Polygamma function.
  
      .. note::
         Forward computation in CPU can not be done if
         `SciPy <https://www.scipy.org/>`_ is not available.
  
      Args:
          n (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
          x (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
  
      Returns:
          ~chainer.Variable: Output variable.
      """
      return PolyGamma().apply((n, x))[0]
  
file_path: chainer/chainer/functions/math/polygamma.py
imports: 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: polygamma(n, x) and returns: PolyGamma