code: def test_forward_gpu_train(self):
      with testing.assert_warns(DeprecationWarning):
          self.rnn.to_gpu()
      with chainer.using_config(
          "use_cudnn", "always"
      ), chainer.using_config("train", True):
          self.check_forward(
              cuda.to_gpu(self.h),
              cuda.to_gpu(self.c),
              [cuda.to_gpu(x) for x in self.xs],
          )
  
imports: 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
label_desc: Use image node_id 4 for calling the TestNStepBiLSTM obj's underlying member method code with example usage: obj.test_forward_gpu_train() without return types