docs: def add_arguments(cls, parser, sys_arg_list=None):
          """
          Callback to add command line options for this plugin to the argparse
          parser.
  
          """
          parser.add_argument('--fixed_cidr', dest="fixed_cidr", required=True,
                              help="specify the route CIDR "
                                   "(only in fixedconf mode)")
          parser.add_argument('--fixed_hosts', dest="fixed_hosts", required=True,
                              help="list of host IPs, separated by ':' "
                                   "(only in fixedconf mode)")
          return ["fixed_cidr", "fixed_hosts"]