code: def test_variable_aggregation_default(
      self, replicator_fn, create_var
  ):
      replicator = replicator_fn()
      if replicator is None:
          self.skipTest("No replicator supplied.")
      v = create_var(replicator)
      self.assertEqual(
          tf.VariableAggregation.ONLY_FIRST_REPLICA, v.aggregation
      )
  
imports: import os
  from absl import logging
  from absl.testing import parameterized
  from sonnet.src import initializers
  from sonnet.src import test_utils
  from sonnet.src.distribute import replicator
  from sonnet.src.distribute import replicator_test_utils
  import tensorflow
label_desc: Use image node_id 2 for calling the ReplicatorTest obj's underlying member method code with example usage: obj.test_variable_aggregation_default(replicator_fn, create_var) without return types