我用discord.py写了一个机器人。问题是它响应我的DM，但不响应我在频道中的消息。有人能帮我吗？

import discord
import requests
import urllib.request
import os
from io import BytesIO
from PIL import Image 
from discord.ext import commands

bot = commands.Bot(command_prefix='!')
@bot.event 
async def on_ready(): 
    print('We have logged in as {0.user}'.format(bot))

@bot.event 
async def on_message(message): 
    await bot.process_commands(message)

@bot.command() 
async def bothello(ctx): 
    print(ctx.channel) 
    if isinstance(ctx.channel, discord.DMChannel): 
        await ctx.send(f'DM') 
    elif isinstance(ctx.channel, discord.TextChannel): 
        print(ctx.channel.name) 
        await ctx.send(f'channel: {ctx.channel.name}') 
    else: 
        print("no way") 
    print('hello')

bot.run('MY_BOT_TOKEN')

我试着修改许可证，但没有用。