code: def forward_expected(self, inputs):
      (x,) = inputs
      expected = numpy.cumprod(x, axis=self.axis)
      expected = force_array(expected)
      return (expected,)
  
imports: import unittest
  import numpy
  from chainer.backends import cuda
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import force_array
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the TestCumprod obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: expected