code: def testCustomReduceFn(self):
      log_accept_ratio = tf.constant([np.log(0.1), np.log(1.0)])
      state = [
          tf.zeros([2]),
      ]
  
      old_step_size = 1.0
      kernel = FakeMHKernel(
          FakeSteppedKernel(step_size=old_step_size),
          log_accept_ratio=log_accept_ratio,
      )
      kernel = sssa.SimpleStepSizeAdaptation(
          kernel,
          num_adaptation_steps=1,
          adaptation_rate=tf.constant(_RATE - 1.0, dtype=tf.float64),
          reduce_fn=tf.reduce_max,
          validate_args=True,
      )
  
      kernel_results = kernel.bootstrap_results(state)
      for _ in range(2):
          _, kernel_results = kernel.one_step(state, kernel_results)
  
      step_size = self.evaluate(
          kernel_results.inner_results.accepted_results.step_size,
      )
  
      # If reduce_fn was left at default, this would have decreased.
      self.assertAllClose(old_step_size * _RATE, step_size)
  
imports: import collections
  import functools
  from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v1
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import normal
  from tensorflow_probability.python.distributions import sample
  from tensorflow_probability.python.experimental.mcmc import sharded
  from tensorflow_probability.python.internal import distribute_lib
  from tensorflow_probability.python.internal import distribute_test_lib
  from tensorflow_probability.python.internal import samplers
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import generic
  from tensorflow_probability.python.mcmc import hmc
  from tensorflow_probability.python.mcmc import kernel
  from tensorflow_probability.python.mcmc import sample
  from tensorflow_probability.python.mcmc import simple_step_size_adaptation
label_desc: Use image node_id 12 for calling the SimpleStepSizeAdaptationTest obj's underlying member method code with example usage: obj.testCustomReduceFn() without return types