old_contents: # 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 keystone.conf import utils
  
  
  driver = cfg.StrOpt(
      'driver',
      help=utils.fmt("""
  Entrypoint for the assignment backend driver in the keystone.assignment
  namespace. Only an SQL driver is supplied. If an assignment driver is not
  specified, the identity driver will choose the assignment driver (driver
  selection based on `[identity]/driver` option is deprecated and will be removed
  in the "O" release).
  """))
  
  prohibited_implied_role = cfg.ListOpt(
      'prohibited_implied_role',
      default=['admin'],
      help=utils.fmt("""
  A list of role names which are prohibited from being an implied role.
  """))
  
  
  GROUP_NAME = __name__.split('.')[-1]
  ALL_OPTS = [
      driver,
      prohibited_implied_role
  ]
  
  
  def register_opts(conf):
      conf.register_opts(ALL_OPTS, group=GROUP_NAME)
  
  
  def list_opts():
      return {GROUP_NAME: ALL_OPTS}
  
new_contents: # 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 keystone.conf import utils
  
  
  driver = cfg.StrOpt(
      'driver',
      help=utils.fmt("""
  Entry point for the assignment backend driver (where role assignments are
  stored) in the `keystone.assignment` namespace. Only a SQL driver is supplied
  by keystone itself. If an assignment driver is not specified, the identity
  driver will choose the assignment driver based on the deprecated
  `[identity]/driver` option (the behavior will be removed in the "O" release).
  Unless you are writing proprietary drivers for keystone, you do not need to set
  this option.
  """))
  
  prohibited_implied_role = cfg.ListOpt(
      'prohibited_implied_role',
      default=['admin'],
      help=utils.fmt("""
  A list of role names which are prohibited from being an implied role.
  """))
  
  
  GROUP_NAME = __name__.split('.')[-1]
  ALL_OPTS = [
      driver,
      prohibited_implied_role
  ]
  
  
  def register_opts(conf):
      conf.register_opts(ALL_OPTS, group=GROUP_NAME)
  
  
  def list_opts():
      return {GROUP_NAME: ALL_OPTS}
  
subject: Improve keystone.conf [assignment] documentation