code: def _to_gpu(x, device_id):
      if device_id >= 0:
          return cuda.to_gpu(x, device_id)
      else:
          return x
  
imports: import unittest
  import numpy
  import pytest
  import chainer
  from chainer import backend
  from chainer.backends import _cpu
  from chainer.backends import cuda
  from chainer import functions
  from chainer import testing
  import chainerx
label_desc: Use image node_id 1 for calling a global function with example usage: _to_gpu(x, device_id) and returns: cuda, x