class_docstr: Adafactor optimizer, as described in https://arxiv.org/abs/1804.04235.
docstr: Default Adafactor second-moment decay schedule.
docstr_tok: ["Default","Adafactor","second-moment","decay","schedule","."]
code: def _decay_rate_pow(i, exponent=0.8):
      """Default Adafactor second-moment decay schedule."""
      t = jnp.array(i, jnp.float32) + 1.0
      return 1.0 - t ** (-exponent)
  
imports: from trax.fastmath import numpy
  from trax.optimizers import base
label_desc: Use image node_id 2 for calling the Adafactor obj's underlying member method code with example usage: obj._decay_rate_pow(i, exponent) and returns: unknown