title: How to purge messages for specific users in Discord.py
body: <p>Hey so I was trying to make a command in discord.py rewrite version was doing something like <code>&gt;purgemessage 5</code> would purge 5 messages of the user who sent that message but for some reason, it won't work. I am using this in a reply so it won't show the error;-; but here is what I have done so far to try to make it work!</p>
  <pre><code># purges author's messages
  @commands.command(name='purgemessage', aliases=['pm'])
  @commands.cooldown(1, 300)
  @commands.has_any_role(OwnerRole, GuildMasterRole, AdminRole, ExclusiveMemberRole)
  async def purgemessage(self, ctx, amount:int, *, arg:str=None):
      msg = []
      channel = ctx.message.channel.history(limit=None)
      async for message in channel:
          if message.author == ctx.message.author:
              msg.append(message)
      await ctx.message.channel.delete_messages(msg)
      await asyncio.sleep(.5)
      botMessage = await ctx.send(f'**{amount}** messages were successfully deleted!')
      await asyncio.sleep(.5)
      await botMessage.delete()
  </code></pre>