class_docstr: Enable tests to request GPU hardware and skip non-GPU combinations.
  
  This class expects test_combinations to be generated with `NamedDistribution`
  wrapping instances of `tf.distribute.Strategy`.
  
  Optionally, the `required_gpus` argument is supported.  GPU hardware is
  required, if its value is `True` or > 0.
  
  Attributes:
    GPU_TEST: The environment is considered to have GPU hardware available if
              the name of the program contains "test_gpu" or "test_xla_gpu".
class_docstr_tok: ["Enable","tests","to","request","GPU","hardware","and","skip","non-GPU","combinations",".","This","class","expects","test_combinations","to","be","generated","with","`","NamedDistribution","`","wrapping","instances","of","`","tf.distribute.Strategy","`",".","Optionally",",","the","`","required_gpus","`","argument","is","supported",".","GPU","hardware","is","required",",","if","its","value","is","`","True","`","or",">","0",".","Attributes",":","GPU_TEST",":","The","environment","is","considered","to","have","GPU","hardware","available","if","the","name","of","the","program","contains","``","test_gpu","''","or","``","test_xla_gpu","''","."]
code: def parameter_modifiers(self):
      return [
          combinations_lib.OptionalParameter("required_gpus"),
          combinations_lib.OptionalParameter("required_physical_gpus"),
      ]
  
imports: import collections
  import copy
  import re
  import sys
  import types
  import unittest
  from absl import app
  import six
  from tensorflow.python.client import session
  from tensorflow.python.distribute import collective_all_reduce_strategy
  from tensorflow.python.distribute import distribute_lib
  from tensorflow.python.distribute import multi_process_runner
  from tensorflow.python.distribute import multi_worker_test_base
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import combinations
  from tensorflow.python.framework import config
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_combinations
  from tensorflow.python.framework import test_util
  from tensorflow.python.platform import flags
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.util import tf_decorator
  from tensorflow.python.util import tf_inspect
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 2 for calling the GPUCombination obj's underlying member method code with example usage: obj.parameter_modifiers() and returns: list