bot discord responde

from discord.ext import commands

client = commands.Bot(command_prefix='!')

@client.event
async def on_ready():
    print('Bot listo')


@client.event
async def on_message(message):
    if client.user.id != message.author.id:
        if 'hola' in message.content: #lo que dira la persona
            await message.channel.send(f"{message.author.mention}" +"Que tal estas?") #Lo que dira el bot

    await client.process_commands(message)

client.run('') #Crear un bot token: https://discord.com/developers/applications