如何在 cog 中发出明确的消息命令

Question

import discord
from discord.ext import commands

class Purge(commands.Cog):
    def __init__(self, client):
        self.client = client

    @commands.command()
    async def clear(ctx, amount = 5):
        if amount == 0:
            await ctx.send("AMOUNT CANNOT BE 0!")
        else:
            await ctx.channel.purge(limit = amount + 1)


def setup(client):
    client.add_cog(Purge(client))

当我输入命令 -clear 时，它不执行任何操作，也没有错误消息告诉我任何事情