text: #   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
  #
  # 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.
  
  from django.conf import settings
  from django.utils import translation
  
  
  def get_preferred_version(request):
      """
      Returns default docs version.
      """
      return settings.DEFAULT_DOCS_VERSION
  
  
  def get_preferred_language(request):
      """
      Observes the user's session, and consequently the cookies,
      to find the preferred documentation language.
      """
  
      default_lang = 'en'
  
      if request.LANGUAGE_CODE == 'zh':
          default_lang = 'zh'
  
      return default_lang
  
  
  def set_preferred_language(request, response, lang):
      """
      Sets the preferred documentation version in the user's session AND cookie.
      """
      translation.activate(lang)
      request.session[translation.LANGUAGE_SESSION_KEY] = lang
      request.LANGUAGE_CODE = lang
  