Help with Slash Commands

Hello there. So, I am an absolute noob when it comes to slash commands, and the documentation doesn't really help me either. That being said, I based my code off of the guide, but it seems to not be working. Here is my code for reference:
const { REST } = require('@discordjs/rest');
const { Routes } = require('discord-api-types/v9');
const { SlashCommandBuilder } = require('@discordjs/builders');

// Place your client and guild ids here
const clientId = 'CLIENT_ID'; // actual client ID here
const guildId = 'GUILD_ID'; // actual guild ID here

const rest = new REST({ version: '9' }).setToken("TOKEN"); // actual token here

(async () => {
    try {
        console.log('Started refreshing application (/) commands.');

        await rest.put(
            Routes.applicationGuildCommands(clientId, guildId),
            { body: [
                new SlashCommandBuilder()
                .setName("message")
                .setDescription("Sends the specified message to the user")
                .addSubcommand(subcommand => 
                    subcommand
                    .setName("blacklist")
                    .setDescription("Informs a user of a LETI blacklist. For use by Command Staff.")
                    .addStringOption(option => option.setName("reason").setDescription("The reason for the blacklist"))
                )
                .addSubcommand(subcommand => 
                    subcommand
                    .setName("suspend")
                    .setDescription("Informs a user of a LETI suspension. For use by Command Staff.")
                ).toJSON()
            ]},
        );

        console.log('Successfully reloaded application (/) commands.');
    } catch (error) {
        console.error(error);
    }
})();

But, whenever I run this, I get the following error (image attached). If someone could help me, that would be amazing. Thank you for your time and help, I appreciate it.
unknown.png
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