Discord js deafening an user

Hello I'm trying to deafen a particular person in discord but I keep getting the following error:

TypeError: message.setDeaf is not a function

The discord js docs state that you should deafen members like this.

.setDeaf(deaf)

Deafen/undeafen a user.

I'm unsure as to why I'm getting this error, below is my code;

var Discord  = require("discord.js");
var client = new Discord.Client();
var user = "30898500862111287"

client.on('ready', () => {
  console.log('I am ready!');
});

client.on('message', function(message) {
  if (message.content === '$deafen') {
    message.setDeaf(user);
  }
});

via fragile