text: # coding=utf-8
  # Copyright 2018 The Google AI Language Team Authors.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """Functions and classes related to optimization (weight updates)."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import chainer
  
  
  class AdamRule(chainer.optimizers.adam.AdamRule):
      def init_state(self, param):
          super(AdamRule, self).init_state(param)
          # Cancel weight decay in `bias` or `layer normalization` paramters
          if param.ndim <= 1:
              self.hyperparam.weight_decay_rate = 0.
  
  
  class WeightDecayForMatrixAdam(chainer.optimizers.Adam):
      def create_update_rule(self):
          return AdamRule(self.hyperparam)
  