code: def mxnet_prefer_gpu():
      
      gpu = int(os.environ.get('MXNET_GPU', default=0))
      if gpu in mx.test_utils.list_gpus():
          return mx.gpu(gpu)
      return mx.cpu()
docs: If gpu available return gpu, else cpu
  
      Returns
      -------
      context : Context
          The preferable GPU context.