code: def forward_expected(self, inputs):
      n, x = inputs
      import scipy
  
      y_expect = scipy.special.polygamma(n, x)
      return (y_expect.astype(self.dtype),)
  
file_path: chainer/tests/chainer_tests/functions_tests/math_tests/test_polygamma.py
imports: import unittest
  import numpy
  import chainer
  import chainer.functions
  from chainer import testing
label_desc: Use image node_id 3 for calling the TestPolyGamma obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: y_expect