old_contents: # Copyright 2016 Hewlett Packard Enterprise Development Company, L.P.
  #
  # 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 oslo_config import cfg
  from oslo_middleware import cors
  
  
  def set_cors_middleware_defaults():
      """Update default configuration options for oslo.middleware."""
      # CORS Defaults
      # TODO(krotscheck): Update with https://review.openstack.org/#/c/285368/
      cfg.set_defaults(cors.CORS_OPTS,
                       allow_headers=['X-Auth-Token',
                                      'X-Openstack-Request-Id',
                                      'X-Subject-Token'],
                       expose_headers=['X-Auth-Token',
                                       'X-Openstack-Request-Id',
                                       'X-Subject-Token'],
                       allow_methods=['GET',
                                      'PUT',
                                      'POST',
                                      'DELETE',
                                      'PATCH']
                       )
  
new_contents: # Copyright 2016 Hewlett Packard Enterprise Development Company, L.P.
  #
  # 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 oslo_middleware import cors
  
  
  def set_cors_middleware_defaults():
      """Update default configuration options for oslo.middleware."""
      cors.set_defaults(
          allow_headers=['X-Auth-Token',
                         'X-Openstack-Request-Id',
                         'X-Subject-Token'],
          expose_headers=['X-Auth-Token',
                          'X-Openstack-Request-Id',
                          'X-Subject-Token'],
          allow_methods=['GET',
                         'PUT',
                         'POST',
                         'DELETE',
                         'PATCH']
      )
  
subject: update default configuration using cors' own set_defaults funtion