text: # coding=utf-8
  # Copyright 2019 The Trax 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.
  
  """SGD optimizer class."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  from trax.optimizers import base as opt_base
  
  
  class SGD(opt_base.Optimizer):
    """Plain SGD optimizer."""
  
    def init(self, params):
      return None
  
    def update(self, step, grads, weights, slots, opt_params):
      del step
      del slots
      learning_rate = opt_params['learning_rate']
      return weights - (learning_rate * grads).astype(weights.dtype), None
  