code: def test_concat_gpu(self):
      self._concat_helper(gpu_dev)
  
imports: from __future__ import division
  import unittest
  import math
  import numpy
  from singa import singa_wrap
  from singa import tensor
  from cuda_helper import gpu_dev, cpu_dev
label_desc: Use image node_id 22 for calling the TestAPI obj's underlying member method code with example usage: obj.test_concat_gpu() without return types