Describe the relationship between columns that can be null and entity subtypes. Under what circumstances would these columns lead to more than one entity subtype?

What did i do wrong with this const discord = require('discord.js'); var bot = new discord.client(); const token = 'ntm3mjcxmtu1mjg3ote2ntq2.dyogew.dpfiwfpuifzuzvifop-csuxasnm' const prefix = "! " bot.registry.registergroup('simple', 'simple'); bot.registry.registerdefaults(); bot.registry. + '/commands'); bot.on('message', message => { if(message.content == 'hi! ') { message.channel.send ('@everyone sup, how is @everyone day going'); } if(message.content == 'h3lp') { message.channel.send ('dose not have any commands yet'); } bot.on('ready', function() { console.log("ready") }); bot.login(token);