code: def forward_expected(self, inputs):
      (x,) = inputs
      expected = numpy.log(numpy.exp(x).sum(axis=self.axis))
      expected = force_array(expected)
      return (expected,)
  
file_path: chainer/tests/chainer_tests/functions_tests/math_tests/test_logsumexp.py
imports: import unittest
  import numpy
  from chainer import functions
  from chainer import testing
  from chainer.utils import force_array
label_desc: Use image node_id 5 for calling the TestLogSumExp obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: expected