在以下OpenStack命令中，有用于添加和更改的“设置”，有用于删除的“删除”的功能，但是为什么没有“显示”选项？
$ nova help meta
usage: nova meta <server> <action> <key=value> [<key=value> ...]
Set or delete metadata on a server.
Positional arguments:
<server> Name or ID of server.
<action> Actions: 'set' or 'delete'.
<key=value> Metadata to set or delete (only key is necessary on delete).