如何在discord.py中制作赋予角色on_message？

import discord
from discord.ext import commands

intents = discord.Intents.default()
intents.members = True

bot = commands.Bot(command_prefix='!', intents=intents)

@bot.event
async def on_ready():
    print(f'Logged in as {bot.user.name}')

@bot.event
async def on_message(message):
    if message.author == bot.user:
        return

    if 'hello' in message.content.lower():
        role = discord.utils.get(message.guild.roles, name='Role Name')
        await message.author.add_roles(role)
        await message.channel.send(f'Role {role.name} assigned to {message.author.mention}')

    await bot.process_commands(message)

bot.run('YOUR_BOT_TOKEN')