code: def available_gpus():
      devices = []
      for device_id in range(num_available_gpus()):
          devices.append("/gpu:{0}".format(device_id))
      return devices
  
imports: import math
  import numpy
  import nvidia.dali.fn
  import nvidia.dali.plugin.tf
  import nvidia.dali.types
  import os
  import tensorflow
  from contextlib import contextmanager
  from nose import SkipTest
  from nvidia.dali.pipeline import Pipeline
  from tensorflow.python.client import device_lib
  from test_utils import to_array, get_dali_extra_path
label_desc: Use image node_id 4 for calling a global function with example usage: available_gpus() and returns: devices