`prefix`: Query or change the bot's command prefix in the server.

    You must have the Manage Server permission to change the bot's prefix.

    Without a prefix set, the bot will use the default command prefix in this
    server. Even with a custom prefix set, this command will always be available
    using the default prefix so that the prefix can be reset or changed to a
    new one if the one it is set to is forgotten or impractical.

    **Usage:**
        `prefix`: State the bot's prefix in this server.
        `prefix PREFIX`: Change the command prefix to `PREFIX`.
        `prefix reset`: Reset the prefix to the default.