Ошибка "init() missing 1 required positional argument: 'command_prefix'" Discord bot

Я создаю бота и столкнуться с проблемой:

Traceback (most recent call last):
File "bot.py", line 4, in client = commands.Bot( commands_prefix = '$') 
TypeError: init() missing 1 required positional argument: 'command_prefix'

Вот мой код:

import discord
from discord.ext import commands

client = commands.Bot( commands_prefix = '$' )

@client.event

async def on_ready():
    print('Bot')

@client.commands ( pass_context = True)

async def hello( ctx):
    await ctx.send('Hello')

token = open ('token.txt', 'r').readline()

client.run (token)