code: def testRegroupCollectionsMapping(self):
      class CollectionsMappingBasedClass(collections.abc.Mapping):
          """Class inherited from collections.abc.Mapping."""
  
          def __init__(self, *args, **kwargs):
              self._d = dict(*args, **kwargs)
  
          def __getitem__(self, key):
              return self._d.__getitem__(key)
  
          def __iter__(self):
              return iter(self._d)
  
          def __len__(self):
              return len(self._d)
  
      result = distribute_utils.regroup(
          (
              CollectionsMappingBasedClass(a="a1", b="b1"),
              CollectionsMappingBasedClass(a="a2", b="b2"),
          )
      )
      self.assertIsInstance(result, CollectionsMappingBasedClass)
      self._is_per_replica(result["a"], ["a1", "a2"])
      self._is_per_replica(result["b"], ["b1", "b2"])
  
imports: import collections
  import collections.abc
  from absl.testing import parameterized
  import wrapt
  from tensorflow.python.distribute import combinations
  from tensorflow.python.distribute import distribute_utils
  from tensorflow.python.distribute import strategy_combinations
  from tensorflow.python.distribute import values
  from tensorflow.python.eager import context
  from tensorflow.python.eager import test
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import ops
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.ops import variable_v1
  from tensorflow.python.saved_model.model_utils import mode_keys
label_desc: Use image node_id 4 for calling the RegroupAndSelectDeviceTest obj's underlying member method code with example usage: obj.testRegroupCollectionsMapping() and returns: self, iter, len