code: def test_forward(self):
      # TODO(unno): We need to test return values of forward function.
      cpu_loss = self.link(
          chainer.Variable(self.x), chainer.Variable(self.t)
      ).data
      with testing.assert_warns(DeprecationWarning):
          self.link.to_gpu()
      gpu_loss = self.link(
          chainer.Variable(cuda.to_gpu(self.x)),
          chainer.Variable(cuda.to_gpu(self.t)),
      ).data
      testing.assert_allclose(
          cpu_loss, cuda.to_cpu(gpu_loss), **self.test_forward_options
      )
  
imports: import copy
  import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
label_desc: Use image node_id 6 for calling the TestBinaryHierarchicalSoftmax obj's underlying member method code with example usage: obj.test_forward() without return types