code: def adafactor_decay_rate_pow(exponent):
      """Second moment decay rate where memory-length grows as step_num^exponent.
  
      Args:
        exponent: a float between 0 and 1
      Returns:
        a scalar
      """
      return 1.0 - tf.pow((step_num() + 1.0), -exponent)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensor2tensor.layers import common_layers
  from tensor2tensor.utils import quantization
  import tensorflow.compat.v1
label_desc: Use image node_id 2 for calling a global function with example usage: adafactor_decay_rate_pow(exponent) and returns: unknown