code: def _piecewise_learning_rate(step, boundaries, values):
      """Scale learning rate according to the given schedule.
  
      Multipliers are not cumulative.
  
      Args:
        step: global step
        boundaries: List of steps to transition on.
        values: Multiplier to apply at each boundary transition.
  
      Returns:
        Scaled value for the learning rate.
      """
      values = [1.0] + values
      boundaries = [float(x) for x in boundaries]
      return tf.train.piecewise_constant(
          step, boundaries, values, name="piecewise_lr"
      )
  
file_path: tensor2tensor/tensor2tensor/utils/learning_rate.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  from tensor2tensor.utils import mlperf_log
  import tensorflow.compat.v1
label_desc: Use image node_id 6 for calling a global function with example usage: _piecewise_learning_rate(step, boundaries, values) and returns: tf