code: def forward(self, inputs, device):
      n, x = inputs
      y = F.polygamma(n, x)
      return (y,)
  
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 4 for calling the TestPolyGamma obj's underlying member method code with example usage: obj.forward(inputs, device) and returns: y