subnet pool can not delete prefixes

[Wenran Xiao]

env: Rocky devstack

I create a subnetpool like this:
[stack@qs11 ~]$ openstack subnet pool show demo-subnetpool4
+-------------------+-------------------------------------------------------------------+
| Field | Value |
+-------------------+-------------------------------------------------------------------+
| address_scope_id | None |
| created_at | 2018-09-17T09:07:04Z |
| default_prefixlen | 26 |
| default_quota | None |
| description | |
| id | ee80a076-ab3a-464d-88bf-a3181c0cf6d8 |
| ip_version | 4 |
| is_default | False |
| max_prefixlen | 32 |
| min_prefixlen | 8 |
| name | demo-subnetpool4 |
| prefixes | 192.168.11.0/24, 198.160.10.0/23, 198.51.100.0/24, 203.0.113.0/24 |
| project_id | 3cc022c8972345aaafc1346343eb4747 |
| revision_number | 6 |
| shared | True |
| tags | |
| updated_at | 2018-09-17T09:52:32Z |
+-------------------+-------------------------------------------------------------------+

The subnet pool have prefixes:
 192.168.11.0/24
 198.160.10.0/23
 198.51.100.0/24
 203.0.113.0/24
The prefixes 198.160.10.0/23 is create by mistake, I try to delete 198.160.10.0/23 prefixes, but I can't find out a method.
usage: neutron subnetpool-update [-h] [--description DESCRIPTION]
                                 [--min-prefixlen MIN_PREFIXLEN]
                                 [--max-prefixlen MAX_PREFIXLEN]
                                 [--default-prefixlen DEFAULT_PREFIXLEN]
                                 [--pool-prefix PREFIXES]
                                 [--is-default {True,False}] [--name NAME]
                                 [--address-scope ADDRSCOPE | --no-address-scope]
                                 SUBNETPOOL

usage: openstack subnet pool set [-h] [--name <name>]
                                 [--pool-prefix <pool-prefix>]
                                 [--default-prefix-length <default-prefix-length>]
                                 [--min-prefix-length <min-prefix-length>]
                                 [--max-prefix-length <max-prefix-length>]
                                 [--address-scope <address-scope> | --no-address-scope]
                                 [--default | --no-default]
                                 [--description <description>]
                                 [--default-quota <num-ip-addresses>]
                                 [--tag <tag>] [--no-tag]
                                 <subnet-pool>

usage: openstack subnet pool unset [-h] [--pool-prefix <pool-prefix>]
                                   [--tag <tag> | --all-tag]
                                   <subnet-pool>
Only have "load prefixes" method.