new_contents: # -*- coding: utf-8 -*-
  
  # Copyright 2017 EMBL - European Bioinformatics Institute
  #
  # 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.
  
  import logging
  
  from rest_framework import viewsets, mixins
  
  logger = logging.getLogger(__name__)
  
  
  class ReadOnlyListModelViewSet(mixins.ListModelMixin,
                                 viewsets.GenericViewSet):
      """
      A viewset that provides default `list()` action.
      """
      pass
  
  
  class ReadOnlyRetrieveModelViewSet(mixins.RetrieveModelMixin,
                                     viewsets.GenericViewSet):
      """
      A viewset that provides default `retrieve()` action.
      """
      pass
  
  
  class ReadOnlyModelViewSet(mixins.RetrieveModelMixin,
                             mixins.ListModelMixin,
                             viewsets.GenericViewSet):
      """
      A viewset that provides default `list()` and `retrieve()` actions.
      """
      pass
  
subject: add common mixins