code: def _validate_aggregation(kwargs):
      aggregation = kwargs.get(
          "aggregation", vs.VariableAggregation.NONE
      )
  
      if aggregation not in (
          vs.VariableAggregation.NONE,
          vs.VariableAggregation.SUM,
          vs.VariableAggregation.MEAN,
          vs.VariableAggregation.ONLY_FIRST_REPLICA,
      ):
          raise ValueError(
              "Invalid variable aggregation mode: %s for variable: %s"
              % (aggregation, kwargs["name"])
          )
      return aggregation
  
imports: from collections import abc
  import contextlib
  import threading
  from tensorflow.python.distribute import distribute_lib
  from tensorflow.python.distribute import tpu_values
  from tensorflow.python.distribute import values
  from tensorflow.python.distribute.reduce_util import ReduceOp
  from tensorflow.python.eager import context
  from tensorflow.python.eager import record
  from tensorflow.python.framework import composite_tensor
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import control_flow_ops
  from tensorflow.python.ops import resource_variable_ops
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.ops.losses import losses_impl
  from tensorflow.python.util import nest
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 14 for calling a global function with example usage: _validate_aggregation(kwargs) and returns: aggregation