docstr: Request GPU with no GPUs available, expecting an exception
docstr_tok: ["Request","GPU","with","no","GPUs","available",",","expecting","an","exception"]
code: def test_gpu_unavailable(self, mock_available):
      """Request GPU with no GPUs available, expecting an exception"""
      mock_available.return_value = False
      self.parser.add_argument(
          "--num_gpus", help="number of gpus to use", type=int
      )
      tf_args = self.parser.parse_args(["--num_gpus", "1"])
  
      with self.assertRaises(Exception):
          map_fn = TFSparkNode.run(
              self.default_fn,
              tf_args,
              self.cluster_meta,
              self.tensorboard,
              self.log_dir,
              self.queues,
              self.background,
          )
          map_fn([0])
  
file_path: TensorFlowOnSpark/tests/test_TFSparkNode.py
imports: import argparse
  import os
  import random
  import unittest
  from tensorflowonspark import gpu_info, reservation, TFSparkNode
  from unittest.mock import patch
label_desc: Use image node_id 4 for calling the TFSparkNodeTest obj's underlying member method code with example usage: obj.test_gpu_unavailable(mock_available) without return types