code: def test_forward_gpu_multi(self):
      with cuda.get_device_from_id(0):
          with testing.assert_warns(DeprecationWarning):
              self.link.to_gpu()
          inputs = [cuda.to_gpu(v) for v in self.inputs]
      with cuda.get_device_from_id(1):
          self.check_forward(*inputs)
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  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 5 for calling the TestTreeLSTM obj's underlying member method code with example usage: obj.test_forward_gpu_multi() without return types