code: def _testCollectiveReduce(
      self,
      inputs,
      expected,
      set_graph_key,
      communication_hint="auto",
      fp16=False,
      instance_key=1,
      merge_op="Add",
      final_op="Div",
      timeout=0,
      reported_group_size=None,
  ):
      group_key = 1
      group_size = len(inputs)
      if reported_group_size is None:
          reported_group_size = group_size
      device_type = "CPU"
      config = config_pb2.ConfigProto(
          device_count={device_type: group_size}
      )
      devices = [
          "/{}:{}".format(device_type, i) for i in range(group_size)
      ]
  
      with self.session(config=config) as sess:
          colred = []
          for i in range(group_size):
              with ops.device(devices[i]):
                  tensor = constant_op.constant(
                      inputs[i],
                      dtype=(
                          dtypes.float16 if fp16 else dtypes.float32
                      ),
                  )
                  colred.append(
                      collective_ops.all_reduce(
                          tensor,
                          reported_group_size,
                          group_key,
                          instance_key,
                          merge_op,
                          final_op,
                          communication_hint=communication_hint,
                          timeout=timeout,
                      )
                  )
          run_options = config_pb2.RunOptions()
          if set_graph_key:
              run_options.experimental.collective_graph_key = 1
          results = sess.run(colred, options=run_options)
      tolerance = 1e-3 if fp16 else 1e-5
      for i in range(group_size):
          logging.info(
              "i {} result {} expected {}".format(
                  i, results[i], expected
              )
          )
          self.assertAllClose(
              results[i], expected, rtol=tolerance, atol=tolerance
          )
  
imports: import time
  from tensorflow.core.protobuf import config_pb2
  from tensorflow.core.protobuf import rewriter_config_pb2
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import config
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import kernels
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import collective_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variable_v1
  from tensorflow.python.ops import variables
  from tensorflow.python.ops import while_loop
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
label_desc: Use image node_id 2 for calling the CollectiveOpTest obj's underlying member method code with example usage: obj._testCollectiveReduce(inputs, expected, set_graph_key, communication_hint, fp16, instance_key, merge_op, final_op, timeout, reported_group_size) without return types