text: from keystone.backends.sqlalchemy import migration
  from keystone.manage2 import base
  from keystone.manage2 import common
  
  
  @common.arg('--version',
      required=True,
      help='specify the desired database version')
  class Command(base.BaseSqlalchemyCommand):
      """Downgrades the database to the specified version"""
  
      @staticmethod
      def downgrade_database(version):
          """Downgrade database to the specified version"""
          migration.downgrade(Command._get_connection_string(), version=version)
  
      def run(self, args):
          """Process argparse args, and print results to stdout"""
          self.downgrade_database(version=args.version)
  